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Open Access

Peer-reviewed

Research Article

Is patient empowerment the key to promote adherence? A systematic review of the relationship between self-efficacy, health locus of control and medication adherence

  • Lilla Náfrádi ,

    Contributed equally to this work with: Lilla Náfrádi, Kent Nakamoto, Peter J. Schulz

    Roles Conceptualization, Data curation, Formal analysis, Methodology, Project administration, Writing – original draft

    lilla.nafradi@usi.ch

    Affiliation Institute of Communication and Health, Università della Svizzera italiana, Lugano, Switzerland

    ⨯
  • Kent Nakamoto ,

    Contributed equally to this work with: Lilla Náfrádi, Kent Nakamoto, Peter J. Schulz

    Roles Conceptualization, Funding acquisition, Project administration, Supervision, Writing – review & editing

    Affiliation Institute of Communication and Health, Università della Svizzera italiana, Lugano, Switzerland

    ⨯
  • Peter J. Schulz

    Contributed equally to this work with: Lilla Náfrádi, Kent Nakamoto, Peter J. Schulz

    Roles Conceptualization, Funding acquisition, Project administration, Supervision, Writing – review & editing

    Affiliation Institute of Communication and Health, Università della Svizzera italiana, Lugano, Switzerland

    ⨯

Abstract

Background

Current health policies emphasize the need for an equitable doctor-patient relationship, and this requires a certain level of patient empowerment. However, a systematic review of the empirical evidence on how empowerment affects medication adherence—the extent to which patients follow the physician’s prescription of medication intake—is still missing. The goal of this systematic review is to sum up current state-of-the-art knowledge concerning the relationship between patient empowerment and medication adherence across medical conditions. As our conceptualization defines health locus of control and self-efficacy as being crucial components of empowerment, we explored the relationship between these two constructs and medication adherence.

Methods

Relevant studies were retrieved through a comprehensive search of Medline and PsychINFO databases (1967 to 2017). In total, 4903 publications were identified. After applying inclusion and exclusion criteria and quality assessment, 154 articles were deemed relevant. Peer-reviewed articles, written in English, addressing the relationship between empowerment (predictor) and medication adherence (outcome) were included.

Findings

High levels of self-efficacy and Internal Health Locus of Control are consistently found to promote medication adherence. External control dimensions were found to have mainly negative (Chance and God attributed control beliefs) or ambiguous (Powerful others attributed control beliefs) links to adherence, except for Doctor Health Locus of Control which had a positive association with medication adherence. To fully capture how health locus of control dimensions influence medication adherence, the interaction between the sub-dimensions and the attitudinal symmetry between the doctor and patient, regarding the patient’s control over the disease management, can provide promising new alternatives.

Discussion

The beneficial effect of patients’ high internal and concurrent physician-attributed control beliefs suggests that a so-called “joint empowerment” approach can be suitable in order to foster medication adherence, enabling us to address the question of control as a versatile component in the doctor-patient relationship.

Citation: Náfrádi L, Nakamoto K, Schulz PJ (2017) Is patient empowerment the key to promote adherence? A systematic review of the relationship between self-efficacy, health locus of control and medication adherence. PLoS ONE 12(10): e0186458. https://doi.org/10.1371/journal.pone.0186458

Editor: Monika R. Asnani, University of the West Indies Faculty of Medical Sciences Mona, JAMAICA

Received: September 28, 2016; Accepted: October 2, 2017; Published: October 17, 2017

Copyright: © 2017 Náfrádi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting Information files.

Funding: This work was supported by the Swiss National Science Foundation (FNS 146 980), http://www.snf.ch/en/Pages/default.aspx. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Medication non-adherence—defined as the extent to which patients take medication in ways other than those prescribed by their health care providers—is a serious obstacle to chronic disease care, with a 50% average prevalence across conditions [1,2]. Non-adherence has numerous patient, physician, medication and health care system related factors [1,2]. Several characteristics of the patients, such as health literacy and medication beliefs influence adherence [1–4]. Empowerment [5]—as an activating force that motivates some people to take their health behavior and management of illnesses into their own hands—is also one of the patient-related factors. Empowerment can be conceived as a personal disposition, referring to the patient’s control and power in the medical context [6] or as a relational concept, emphasizing the existing equity in the physician-patient relationship [7]. A collaborative doctor-patient relationship can improve patient empowerment, i.e. the lack of concordance between doctors and patients can lead to paternalism, and negotiated care can bring power balance into the medical relationship [8]. As a matter of fact, the physicians by facilitating patient engagement in the communication process can foster patient empowerment and better patient outcomes [9].

Patient empowerment has been associated with positive health and clinical outcomes since the concept made its mark in health care literature [5,10,11]. The outcomes considered [12] include improved disease management [13–17], effective use of health services [13–15,18], improved health status [19–21], and medication adherence [22,23]. The association between empowerment and positive health behavior and clinical outcomes generally rests on the assumption that patient autonomous activity is beneficial for their health condition. However, in the case of medication adherence, this assumption might not always hold true. Highly empowered patients might believe that they can make treatment decisions more or less by themselves overruling the physician’s prescription. Indeed, intelligent non-adherence is becoming a common term in the adherence literature, referring to patients´ intentional non-adherence based on rational reasons, such as misdiagnosis or side-effects [24]. This definition presupposes that non-adherence in case of these patients is the “right” choice which leads to beneficial health outcomes, i.e. the patients are adequately health literate (having necessary knowledge and decision-making skills about the medical treatment [25,26] to judge whether adhere or not to the prescribed medication regimen. Similarly, Bader et al. (2006) defined critical adherence as the patients’ freedom to elect to interrupt or forgo a therapy, based on an autonomous evaluation [27]. On the one hand, these forms of non-adherence are often viewed as necessary, since adherence is favorable only if the medication is beneficial. On the other hand, if such a high level of patient autonomy is not accompanied by an equally high level of health literacy, the patient might be inclined to non-adherence in a presumptuous manner putting his/her health into jeopardy [25]. Indeed, a recent review [28] investigating the consequences of increasing patient empowerment reported that a high level of patient empowerment had a controversial relationship with adherence. Some aspects of patient empowerment (such as information search and knowledge) promote adherence, while others (i.e. decision participation) reduce therapy adherence [28]. These challenges call for all concerned to review the empirical knowledge available on the relationship between empowerment and adherence.

A multidimensional conceptualization proposed originally in management literature [29,30], and adapted to the health context by Schulz and Nakamoto [31], perceives empowerment as a motivational construct, holding that patients participate as autonomous actors in health care decisions and consequentially take increased responsibility for such decisions [31]). This concept has four components: 1. Meaningfulness (refers to the value of activities), 2. Competence (belief in one’s own capabilities), 3. Impact (belief in making a difference), and 4. Self-determination (refers to the extent to which a choice is characterized by autonomous initiation). Based on this conceptualization, in the present review, patient empowerment is operationalized as patients’ perceptions of their own capacity for disease management and their beliefs about how much control they have over their own health outcomes. This definition leads to two main constructs constituting empowerment, which have been widely studied in medication adherence literature: self-efficacy and health locus of control.

Self-efficacy is strongly related to the Competence dimension of the empowerment concept. Self-efficacy draws on social-cognitive theory and can be defined as the individual’s belief in his/her own ability to implement a specific behavior or a set of behaviors [32]. It can refer to general [33] or context-specific perceptions of one´s own capacity to mobilize resources and motivation to deal with certain situations and challenges [33]. General self-efficacy refers to a stable sense of personal competence across situations [34,35]. It has been shown that a high sense of efficacy can be associated with better health outcomes, greater achievement and better social integration [32,36]. Moreover, self-efficacy was found to be the cornerstone of medication adherence in chronic mental illness [37] and the most prominent factor of adherence across conditions within the socio-cognitive and self-regulation theories [38].

Health locus of control (HLOC) considers whether an individual’s source of reinforcement for health-related behavior is internal or external. The former relates to a high, the latter to a low level of Impact and Self-determination. The operationalization of the construct has since gone through significant changes. A first approach by Rotter (1966) considered Internal (ILOC) and External locus of control (ELOC) as two endpoints of a one-dimensional continuum [39]. ILOC means that the individual’s sense of control over their health is directly related to their own actions, while ELOC refers to the perception that one’s health is determined by external factors. A later conceptualization, the Multidimensional Health Locus of Control (MHLOC), kept internality (Internal HLOC), but divided external locus of control (External HLOC) into specified sub-dimensions: Powerful Others, Doctor, Chance and God HLOC [40,41]. HLOC has been widely used as a predictor of health behavior. Generally, it is assumed that people with high Internal HLOC are more likely to behave in healthier ways than those who do not believe that they have control over their health. However, an extremely high level of Internal HLOC has been proposed to be problematic [42]. By contrast, someone with high scores on the Chance HLOC subscale, believing that it is fate or chance that determines his/her health status, is probably less likely to implement recommended health behavior. Powerful Others HLOC is generally not assumed to encourage health behavior, except if others are supportive of engaging in healthy behavior [43–45]. Wallston (2005) suggested incorporating other variables such as self-efficacy as potential moderators when investigating how HLOC influences health behavior [45]. This suggestion goes hand in hand with our empowerment concept as it incorporates self-efficacy and health locus of control.

The role of patient empowerment in influencing medication adherence is a cardinal question with major practical implications across all clinical and policy levels. Therefore, the present systematic review seeks to answer the question, whether high level of patient empowerment is associated with greater medication adherence. Thus, the goal is to assess the relevant empirical findings about the relationship between patient empowerment and medication adherence across medical conditions. Medication non-adherence was defined as the extent to which the patients do not agree with/follow the physician’s recommendations regarding taking the prescribed medication, measured by self-report, objective measures or mixed indicators. As empowerment is regarded as consisting of HLOC and self-efficacy, we will address their influence on medication adherence in two separate steps.

Materials and methods

Inclusion and exclusion criteria

The studies had to meet the following criteria in order to be included in the present systematic review: (1) peer-reviewed articles, (2) written in English, (3) studies having observational or experimental design, (4) addressing the relationship between medication adherence and at least one aspect of empowerment, (5) empowerment should be considered either as an independent variable or as a mediator, (6) medication adherence had to be assessed as an outcome variable and (7) studies including an adult sample. We excluded papers which were not available in English, included a sample of youth, or focused on over the counter medications. Moreover, qualitative studies, commentaries, essays, study protocols, literature reviews, conceptual papers and conference abstracts were also excluded.

Search strategy

In order to select a proper search strategy, a set of keywords was identified based on a prior scoping search identifying the relevant academic jargon. Therefore, we initially searched several databases including PROSPERO, COCHRANE library, Medline and PsychInfo for review articles related to medication adherence and/or empowerment. Subsequently, a Thesaurus and a PubMesh search was conducted in order to complete the list. In the main search, key terms referring to empowerment and its related constructs were combined with either words related to medication adherence or misuse. In order to include as many variants of the key terms as possible, a wildcard search was used where this was deemed necessary. Keywords were connected via the following Boolean operators: ‘Empowerment’ AND ‘Medication’ AND (‘Adherence’ OR ‘Misuse’) (see: Table 1).

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Table 1. The Boolean search strategy applied in the present systematic review.

https://doi.org/10.1371/journal.pone.0186458.t001

In order to identify relevant articles, two online databases were searched, one with a medical orientation (Medline) and the other with a focus on social sciences (PsychInfo). The search included the literature published since 1966 to May 2017 in Medline and the publications in the time period between 1967 to May 2017 in PsychInfo.

Data analysis and synthesis

The review was prepared in accordance with the PRISMA statement [46] (S1 Table). The original search was carried out by one of the authors (L.N.), and yielded 4903 hits, which were then screened on the basis of the titles and abstracts using three coders for their relevance, applying the above-mentioned inclusion criteria. The interrater agreement was adequate (Cohen’s kappa = 0.95) regarding which publications were deemed relevant and included for full text assessment. A 13-item checklist developed by Wallace et al. (2006) was applied to assess the quality of the included studies. The checklist contains specific questions in order to assess whether the authors provide a clearly defined research question and appropriately describe the theoretical background. Further questions probe the rigor of study design, data collection, data analysis and the solidness of the derived conclusions [47]. The scores ranged from 0 to 13. The interrater agreement regarding the quality of the papers was 79%. The interrater agreement was calculated based on 10% of the hits, which is the recommended ratio of articles to be coded by independent coders according to rule of thumb [48]. Relevant data, such as information regarding the sample, methodology, the included measurement tools and outcomes were extracted based on a previously developed coding scheme. In the case of the data extraction, the interrater agreement was 85.6%. The coders of the abstract screening, data extraction and quality assessment included one of the authors (L.N.) and research assistants with a health communication background. Meta-analysis was not considered to be appropriate as the included studies demonstrated large heterogeneity in terms of the conceptualization and operationalization of empowerment as well as medication adherence [49].

Results

154 articles were deemed to be fit for inclusion based on the full text analysis. None of the studies were judged to have a quality so poor that they had to be excluded. The average quality score was 11.93 out of 13 (SD = 1.6). If the articles reported more than one outcome about the relationship between the empowerment-related constructs and adherence, each result was included separately in the review. Fig 1 provides an overview of the selection process.

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Fig 1. Flow diagram of the study selection process, adapted from Moher et al. (2009).

https://doi.org/10.1371/journal.pone.0186458.g001

Overview of the results

The vast majority of the studies were conducted in North America (n = 107). Other studies took place in Europe (n = 25), Asia (n = 11), Eurasia (n = 1), Australia) (n = 5), South America (n = 4) and Africa (n = 1).

The studies involved patients diagnosed with various disease groups: HIV/AIDS (n = 52), heart and vascular disorders (n = 18), respiratory diseases (n = 15), renal (n = 12) and of the endocrine system (n = 11). Some studies involved participants suffering from diseases of the brain and nervous system (n = 8), musculoskeletal (n = 6) and digestive system (n = 4), cancer (n = 4) and other conditions (n = 17). A small number of studies concerned patients diagnosed with psychological conditions (n = 7). S2 Table provides an overview of the sample characteristics.

We identified numerous scales measuring a given dimension of empowerment based on our operational definition. As far as locus of control is concerned, most of the studies applied either a one dimensional (RIELCS) [39] or a multidimensional measurement (MHLOC Scale) [40] of the concept. Our search revealed studies using several types of self-efficacy beliefs: medication adherence, disease-management, general, coping self-efficacy, etc. Only a minority of the included articles focused on other empowerment-related constructs, such as competence or self-regulation.

Concerning the operationalization of medication adherence, we can distinguish three types: objective measures (using pill count, patients’ medical outcomes or pharmacy records as a proxy of adherence), subjective measures i.e. where patients provided self-reported questionnaires or structured interviews, and lastly mixed measures which apply subjective and objective adherence measures simultaneously. As there is no agreement on a single method which performs well across all criteria [50], we decided to include all of the studies regardless of the adherence measure applied. See S3 Table for an overview of the included studies and S4 Table for their quality assessment score.

The relationship between self-efficacy and medication adherence

The identified studies addressing the relationship between adherence and self-efficacy focused mainly on medication adherence, disease-management and general self-efficacy (See: Table 2).

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Table 2. The relationship found between different types of self-efficacy and medication adherence (N = 92).

https://doi.org/10.1371/journal.pone.0186458.t002

Medication adherence self-efficacy refers to a belief in the patient’s capacity to follow a prescribed medical regimen in challenging situations [51]. Most of the articles (59 out of 66 studies) found a positive link between medication adherence self-efficacy and adherence [52–100], and among these 9 studies also reported that self-efficacy had a mediator role [101–110]. Only three studies considered adherence-self-efficacy solely as a mediator [111–113] and four reported no relationship [114–117].

Disease management self-efficacy refers to the patients’ beliefs in their capacity to manage disease in general [118,119) or condition-specific self-management behavior [120,121]. The studies investigating the relationship between disease management self-efficacy and medication adherence applied specific scales developed to measure efficacy beliefs about implementing tasks related to managing a given condition. The majority of the studies (16 out of 20) reported a positive association [118,122–136], while only 3 reported no relationship [119,137,138] and 1 suggested mixed results [139].

General self-efficacy refers to one’s perceived competence across a wide array of life domains (36). General self-efficacy had, in most of the cases (4 studies out of 6), a positive association with adherence [140–143], while 2 studies did not find any relationship [144,145]. Some studies simultaneously applied general as well as disease or drug specific self-efficacy measures and investigated which one was more likely to predict self-reported adherence to medication. Two of the studies reported that disease specific self-efficacy was a more important predictor of adherence than generic self-efficacy [142,146]; the third study reported no relationship [145].

Studies focusing on other domain-specific self-efficacy measures reported a positive link between adherence and self-efficacy in patient-physician interactions [147,148], coping self-efficacy [149], bi-cultural self-efficacy [150], self-efficacy for managing negative mood, adhering to medication, symptoms and fatigue management, communicating with health care providers and getting support from others [151]. Self-efficacy when disclosing drug use to providers and for safer drug use were not as effective predictors of self-reported adherence as adherence self-efficacy [52]. Self-efficacy scores for physical function were seen to have a negative link to adherence[145].

Concerning the different adherence measures, a positive association between self-efficacy and adherence was reported in a greater proportion in studies using subjective (87%) or mixed measures (79%), compared to studies applying objective adherence measures (66.6%).

The relationship between HLOC and medication adherence

HLOC was predominantly measured using two instruments: the one-dimensional RIELCS measure [39] and the MHLOC [41,152,153], which is a multidimensional instrument.

First, we considered the relationship between the RIELCS and medication adherence. Of the 9 studies, in four cases (45%) ILOC was found to be more beneficial for medication adherence than ELOC [154–157]. By contrast, two studies (22%) found that ELOC was related to better medication adherence than ILOC [158,159]. Finally, in three (33%) studies, ILOC and ELOC orientation did not distinguish between compliant and non-compliant patients [160–162].

The results which relate to MHLOC dramatically differ in terms of its sub-dimensions: Internal HLOC and External HLOC. Many studies (10 out of 26 studies) reported a positive association between Internal HLOC and adherence [81,101,163–170]; only a single study found a negative relationship [171]. Another study reported that a high level of Internal HLOC promotes critical adherence or non-adherence, i.e. how patients decided to follow or forgo a therapy based on autonomous evaluation [27]. There was a high number of null findings, i.e. 15 studies reported no relationship between IHLOC and adherence [160,172–185].

Examining the MHLOC External sub-dimensions respectively (i.e. Chance, God, Powerful others and Doctor HLOC) allowed us to explore and compare their variable associations with adherence. A large enough proportion of the studies (5 out of 18) found a negative link between Chance HLOC and adherence [170,183,186–188], while only one study reported a positive relationship (189). Twelve studies reported null findings [172,174–177,179,180,182,183,185,190,191]. God HLOC had a negative association with medication adherence [172]. In the case of the Powerful others HLOC, the findings are ambiguous, as the number of studies reporting a negative relationship with adherence [169,181,183,192,193] is only slightly higher (5 studies) than the studies which found a positive link (4 studies) [171,189,194,195]. In addition, 11 studies reported no relationship [172,174–177,180,182–184,191,196]. Doctor HLOC, by contrast, seems to promote adherence, as studies unequivocally found that people characterized with high Doctor HLOC tend to comply better with their given medical regimen (3 studies) [169,172,194]. However, in this case 3 studies also found no association with adherence [174,183,197] (see: Table 3).

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Table 3. The relationship between MHLOC and adherence (N = 71).

https://doi.org/10.1371/journal.pone.0186458.t003

The studies applying subjective adherence measures reported more association either in a positive or negative direction (58.5%) between the HLOC dimensions and adherence compared to the studies applying mixed (14.3%) or objective (40%) adherence measures.

HLOC can also be conceived as a mediator of the relationship between adherence and various other predictors, such as perceived necessity of the treatment [198], social support [199], self-efficacy and outcome expectancy [200], competence [175,201] and hostility [202]. Alternatively, MHLOC can also explain to what degree any identified medication non-adherence is deliberate [203].

Health condition-specific patterns

Regarding the role of self-efficacy in predicting adherence across health conditions, in patients diagnosed with digestive system or musculoskeletal diseases, multiple sclerosis, epilepsy, headache and psychiatric conditions, all studies reported a positive association between adherence and self-efficacy. In HIV, respiratory diseases, cancer, heart and vascular disorders, diabetes and renal diseases, the majority of the studies reported a positive association between adherence and self-efficacy, but there were some null findings, too.

Concerning how HLOC affects medication adherence, the studies involving patients diagnosed with HIV, cancer, diabetes and digestive system diseases reported that Internal HLOC fosters, while External HLOC dimensions appear to hinder adherence. In other conditions, the relationship between adherence and HLOC was more ambigous, i.e. in heart and vascular disorders and mental conditions. Besides Internal HLOC, high levels of Doctor HLOC emerged as a significant predictor of greater adherence in two conditions: respiratory diseases [172,194] and renal disease [169,201].

Other important predictors of adherence were the patients’ autonomy preference regarding respiratory diseases [204], perceived autonomy among renal transplant patients [205], self-regulation in heart failure patients [206] and perceived competence [207], autonomous motivation [180,207] and treatment-related empowerment [208] in HIV. In patients diagnosed with diabetes, perceived competence [209], diabetes empowerment [22] and Diabetes HLOC [210] were predictors of adherence.

Discussion

In the present study, the relationship between patient empowerment and medication adherence was reviewed, with special focus on the two constructs deemed to be the central facets of empowerment: HLOC and self-efficacy.

An overview of the relationship between self-efficacy and adherence

Our results confirm that self-efficacy is a strong predictor of medication adherence. Positive association with adherence holds for of all types of self-efficacy: general, medication adherence, disease management and other domain specific measures. Our findings confirm and expand the findings of McCann et al.’s review [37], which highlighted the importance of self-efficacy in medication adherence in chronic mental illness, as we found that self-efficacy was an important predictor of adherence both in the case of mental and somatic diseases. On the one hand, the effect of self-efficacy in fostering adherence is so robust that it holds regardless of the type of self-efficacy applied and across all medical conditions. On the other hand, specific measures of both medication adherence self-efficacy and disease management self-efficacy show a positive association with adherence compared to general self-efficacy more consistently. Thus, future research might apply context-specific measures for predicting medication adherence, considering that the most consistent adherence self-efficacy seems to be associated with adherence. However, this strong link might arise from the operational overlap between these constructs, as medication adherence questionnaires sometimes measure barriers to medication adherence, such as certain aspects of adherence self-efficacy [50].

The relationship between HLOC and adherence

The findings show that Internal HLOC predominantly has a positive link with medication adherence, while External HLOC dimensions have variable associations.

Studies applying the one-dimensional RIELCS [39] showed a trend suggesting that ILOC is more favorable for adherence than ELOC, but the difference was small. The characteristics of this measure might account for the contradicting findings, as the RIELCS does not distinguish the dimensions of ELOC, and this might lead to individual differences in the interpretation. Alternatively, treating ILOC and ELOC as opposite ends of one continuum may not capture its effect on adherence. Therefore, the MHLOC Scale [40] seems to be a more appropriate tool when examining the relationship between HLOC and adherence.

As far as MHLOC is concerned, a clear majority of the studies reported a positive relationship between Internal HLOC and adherence, which confirms that patients’ beliefs of being in control of their own health (a facet of high empowerment) is associated with greater adherence. However, the relationship between External HLOC and adherence is variable, as the sub-facets of HLOC show variable relationships with adherence. In accordance with our assumptions, Chance HLOC, which can signal low empowerment, showed a negative association with medication adherence. God HLOC also had a negative link to adherence, but only one study looked into this relationship [172]. The number of studies reporting a positive and a negative association between Powerful others HLOC and adherence were almost equal. The effect of Powerful others HLOC on adherence might depend on whether these others support or discourage the patients to adhere [43–45]. Indeed, Doctor HLOC seems to be the most beneficial element of External HLOC promoting adherence, especially when it was concurrent with high Internal HLOC [169]. The variable associations of different External HLOC dimensions with medication adherence indicate that the perceived control dimension of empowerment is far from homogenous. In particular, Doctor HLOC fosters adherence, highlighting how, in a medication management context, not only the belief in one’s own ability and control are beneficial, but also acknowledging the medical expertise and the doctor’s influence on one’s health can be auspicious.

Therefore, to fully understand the relationship between HLOC beliefs and adherence, examining solely the main effects of the sub-dimensions may not be sufficient, but looking into the interaction effects between Internal HLOC and External HLOC as well as External HLOC subdimensions on medical regimen adherence might be more fruitful [167,211]. Some studies recognized the importance of the interactional component of patient empowerment, therefore they addressed how the attitudinal symmetry in the doctor-patient dyads regarding patients’ control over health outcomes influenced medication adherence [212,213]. Indeed, patients who held highly similar beliefs to their physicians regarding a patients’ degree of control over their own health, adhered more to their medication regimen than patients who believed more strongly in their own personal control over their health than their doctor did [213].

More than half of the studies report no link between HLOC and medication adherence. Wallston suggested that HLOC does not operate alone to determine a behavior [44], and that other factors such as self-efficacy should be incorporated as a moderator [45]. This idea is compatible with the empowerment concept, which emphasizes that these constructs can jointly explain health behavior such as adherence. The findings seem robust and applicable across different cultures and countries. However, the North American sample may be considered overly representative in this review (close to 70%); therefore, an international or cultural comparison may not be well-grounded or representative here. Moreover, the majority of the sample being North American may have impacted findings, since the health care system in the United States is characterized by an advanced state of technology, private markets and pluralism [214]. Patients in the US are expected to decide about purchasing a health insurance plan choosing from various for-profit commercial insurance companies or from non-profit insurers [214] based on several factors (e.g. premium, deductible and out-of-pocket costs), which might foster patient empowerment compared to countries with a single nationwide system of health insurance.

‘Joint empowerment’ as a facilitator of adherence: Theoretical, operational and policy implications

The review suggests that a shift might be necessary in the conceptual as well as the operational ways of considering patient empowerment. The current literature offers two seemingly opposite approaches: conceiving empowerment as a relational [7] versus an intrapersonal concept [6]. Our findings suggest that in the medication adherence context the individual and relational aspects of empowerment should be viewed as the two sides of the same coin. We argue that patients need a high level of self-efficacy and internal health control beliefs, but they also have to be capable of sharing the control over their disease management with the physician. If we conceptualize empowerment in the above described manner, that would require further research to capture the relational empowerment as a dynamic feature of the doctor-patient relationship unfolding during the medical encounter. On the individual level, that would also require a shift from understanding empowerment as patient autonomy to a framework which would consider it as the patients’ perceived capability to cooperate effectively with the physician and sharing control with him/her. More research would be necessary to discover the right amount of control assigned to the patient and to the physician in the different contexts, i.e. in different conditions or stages of the illness, etc.

The theoretical shift suggested above would call for an operational revolution of empowerment, i.e. developing new measures about the patients’ beliefs about being able to collaborate and discuss issues with the physician, and asking for advice when necessary. As this definition of empowerment unavoidably presupposes the need of the patients’ ability to judge when they can act autonomously and when they would be better off asking for guidance from the physician, it raises the question of whether such a high level of empowerment is beneficial without the necessary health literacy skills [215].

To sum up, patient empowerment can promote medication adherence, but it requires a co-constructed sense of control in the doctor-patient dyad. This has implications for the clinical practice and policy making, i.e.instead of forcing or reinforcing the vision of an overly empowered patient (which can be burdensome for some patients [216,217] and demanding for many health care providers), an equilibrium should be established, in which both parties are interchangeably in control. This requires the health care providers facilitating patient empowerment (internal HLOC and self-efficacy), but also pointing out the importance of relying on the medical expertise of the physicians (Doctor HLOC) while choosing together the best possible treatment. As finding this equilibrium might be challenging, it requires building a strong collaborative doctor-patient relationship and continuous negotiation during the medical encounter. Moreover, patients’ level of health literacy should be taken into account and facilitated, as a recent paper showed that empowerment has a stronger link to better health status among the adequately health literate patients [218]. Most importantly, this approach has the capacity to reconcile the notion of an empowered patient and the shared decision making framework [219], without raising the dilemma of power or imbalanced control in the doctor-patient relationship.

Limitations

This systematic review is not without limitations. First, our approach might not have captured other conceptualizations of empowerment existing in relevant literature. Second, no quantitative value can be presented to demonstrate the relationship between empowerment and medication adherence, as neither of the concepts is currently operationalized consistently across studies, which would allow us to conduct a meta-analysis. Thirdly, the medication adherence measures only rarely distinguish between the intentional and unintentional dimensions of non-adherence, possibly leading to a cancelling out of the relationship between empowerment and intentional non-adherence, with the inclusion of unintentional non-adherence. Studies using objective measures more often reported null findings compared to studies applying subjective adherence measures, introducing potential measurement bias to the analysis. Fourthly, the vast majority of the included studies had a cross-sectional correlational design, therefore we cannot draw any causal inference regarding the relationship between empowerment and adherence from them. Moreover, we included observational and interventional studies together in the systematic review, which introduces substantial heterogeneity. However, given the importance of findings emerging from interventional studies for the practical implications and insights gained in causal relationships, including intervention studies might merit particular prominence. Furthermore, we may unavoidably have missed unpublished studies or those that were not captured by the search strategy, potentially leading to publication bias. However, we put a great effort into avoiding publication bias with such preventative measures as searching without limiting by outcome [220]. The study samples were heterogeneous regarding characteristics such as medical condition, age and education, which may have affected the results. The applied quality assessment checklist did not recommend a cut-off score for low quality, thus all studies with different quality scores were included in the final analysis. Lastly, we included only papers published in the English language, and this might have resulted in missing some relevant work written in other languages.

Conclusions

Our findings indicate that a balanced view would be the most beneficial for facilitating adherence, one alongside which the patients’ beliefs in their own capacity and control over their health is simultaneously present with their acknowledgment of the physician’s role in their disease management. The integration of the relational and individual nature of the construct to a so-called ‘joint empowerment’ approach enables us to address the question of control as a versatile component in a doctor-patient dyad.

Acknowledgments

The authors wish to thank colleagues and research assistants for their help with the data extraction and quality assessment of the various papers.

References

  1. 1. Brown MT, Bussell JK. Medication adherence: WHO cares? Mayo Clin Proc. 2011;86:304–14. pmid:21389250
  2. 2. De Geest S, Sabaté E. Adherence to long-term therapies: Evidence for action. Eur J Cardiovasc Nurs. 2003;2:323. pmid:14667488
  3. 3. McHorney CA, Zhang NJ, Stump T, Zhao X. Structural equation modeling of the proximal-distal continuum of adherence drivers. Patient Prefer Adherence. 2012;6:789–804. pmid:23204839
  4. 4. Tibaldi G, Clatworthy J, Torchio E, Argentero P, Munizza C, Horne R. The utility of the Necessity—Concerns Framework in explaining treatment non-adherence in four chronic illness groups in Italy. Chronic Illn. 2009;5:129–33. pmid:19474235
  5. 5. Rappaport J. Terms of empowerment/exemplars of prevention: Toward a theory for community psychology. Am J Community Psychol. 1987;15(2):121–48. pmid:3604997
  6. 6. Rissel C. Empowerment: the holy grail of health promotion? Health Promot Int. 1994;9(1):39–47.
  7. 7. Sherwin S. No longer patient: Feminist ethics and health care. Philadelphia: Temple Univ Press; 1992.
    • 8. Goodyear-Smith F, Buetow S. Power issues in the doctor-patient relationship. Heal Care Anal. 2001;9(4):449–62.
    • 9. Roter D. Empowering patient communication. In: Kahan S, Gielen AC et al., editors. Baltimore, MD, US: Johns Hopkins University Press; 2014. p. 473–84.
      • 10. Rappaport J. In praise of paradox: A social policy of empowerment over prevention. Am J Community Psychol. 1981;9(1):1–25. pmid:7223726
      • 11. Zimmerman MA, Rappaport J. Citizen participation, perceived control, and psychological empowerment. Am J Community Psychol. 1988;16(5):725–50. pmid:3218639
      • 12. World Health Organization. (Wallerstein N) What is the Evidence on Effectiveness of Empowerment to Improve Health? 2006, p37.
        • 13. Lorig KR, Sobel DS, Ritter PL, Laurent D, Hobbs M. Effect of a self-management program on patients with chronic disease. Eff Clin Pract. 2001;4(6):256–62. pmid:11769298
        • 14. Lorig KR, Ritter PL, González VM. Hispanic chronic disease self-management: a randomized community-based outcome trial. Nurs Res. 2003;52(6):361–9. pmid:14639082
        • 15. Lorig KR, Ritter P, Stewart AL, Sobel DS, BW B Jr, Bandura A, et al. Chronic disease self-management program: 2-year health status and health care utilization outcomes. Med Care. 2001;39(11):1217–23. pmid:11606875
        • 16. Endicott L, Corsello P, Prinzi M, Tinkelman DG, Schwartz A. Operating a sustainable disease management program for chronic obstructive pulmonary disease. Lippincotts Case Manag. 2003;8(6):252–4. pmid:14646783
        • 17. Roberts KJ. Patient empowerment in the United States: a critical commentary. Heal Expect. 1999;2(2):82–92.
        • 18. Tsay S-L, Hung L-O. Empowerment of patients with end-stage renal disease—a randomized controlled trial. Int J Nurs Stud. 2004;41(1):59–65. pmid:14670395
        • 19. Bergsma LJ, Carney ME. Effectiveness of health-promoting media literacy education: a systematic review. Health Educ Res. 2008;23(3):522–42. pmid:18203680
        • 20. Bergsma LJ. Empowerment Education The Link between Media Literacy and Health Promotion. Am Behav Sci. 2004;48(2):152–64.
        • 21. Wallerstein N. What is the evidence on effectiveness of empowerment to improve health? [Health Evidence Network Report]. Copenhagen: World Health Organization Regional Office for Europe; 2006.
          • 22. Hernandez-Tejada MA, Campbell JA, Walker RJ, Smalls BL, Davis KS, Egede LE. Diabetes Empowerment, Medication Adherence and Self-Care Behaviors in Adults with Type 2 Diabetes. Diabetes Technol Ther. 2012;14(7):120423110411000.
          • 23. Webb DG, Horne R, Pinching AJ. Treatment-related empowerment: preliminary evaluation of a new measure in patients with advanced HIV disease. Int J STD AIDS. 2001 Feb;12(2):103–7. pmid:11236098
          • 24. Britten N. Patients’ ideas about medicines: a qualitative study in a general practice population. Br J Gen Pract. 1994;44(387):465–8. pmid:7748635
          • 25. Schulz PJ, Nakamoto K. Health literacy and patient empowerment in health communication: The importance of separating conjoined twins. Patient Educ Couns. 2013;90(1):4–11. pmid:23063359
          • 26. Sørensen K, Van den Broucke S, Fullam J, Doyle G, Pelikan J, Slonska Z, et al. Health literacy and public health: A systematic review and integration of definitions and models. BMC Public Health. 2012;12(1):80.
          • 27. Bader A, Kremer H, Erlich-Trungenberger I, Rojas R, Lohmann M, Deobald O, et al. An adherence typology: coping, quality of life, and physical symptoms of people living with HIV/AIDS and their adherence to antiretroviral treatment. Med Sci Monit. 2006;12(12):CR493–500. pmid:17136004
          • 28. Prigge JK, Dietz B, Homburg C, Hoyer WD, Burton JL. Patient empowerment: A cross-disease exploration of antecedents and consequences. Int J Res Mark. 2015;32(4):375–86.
          • 29. Thomas KW, Velthouse BA. Cognitive elements of empowerment: An “interpretive” model of intrinsic task motivation. Acad Manag Rev. 1990;15(4):666–81.
          • 30. Spreitzer G. Psychological Empowerment in the Workplace: Dimensions, Measurement, and Validation. Academy of Management Journal. 1995. p. 1442–65.
          • 31. Schulz PJ, Nakamoto K. “Bad” literacy, the Internet, and the limits of patient empowerment. 2011 AAAI Spring Symposium Series. 2011.
            • 32. Bandura A. Self-efficacy: toward a unifying theory of behavioral change. Psychological Review. 1977. 191–215. pmid:847061
            • 33. Scholz U, Gutiérrez Doña B, Sud S, Schwarzer R. Is General Self-Efficacy a Universal Construct? Eur J Psychol Assess. 2002;18(3):242–51.
            • 34. Schwarzer R, Jerusalem M. Skalen zur Erfassung von Lehrer-und Schülermerkmalen. Dokumentation der Psychom Verfahren im Rahmen der Wissenschaftlichen Begleit des Model Selbstwirksame SchulenBerlin. 1999;
            • 35. Sherer M, Maddux JE, Mercandante B, Prentice-Dunn S, Jacobs B, Rogers RW. The self-efficacy scale: Construction and validation. Psychol Rep. 1982;51(2):663–71.
            • 36. Jerusalem M, Schwarzer R. Self-efficacy as a resource factor in stress appraisal processes. In Schwarzer R. (Ed.), Self-efficacy: Thought control of action (pp. 195–213). Washington DC: Hemisphere.
              • 37. McCann TV, Clark E, Lu S. The self-efficacy model of medication adherence in chronic mental illness. J Clin Nurs. 2008;17(11c):329–40. pmid:26327416
              • 38. Holmes EA, Hughes DA, Morrison VL. Predicting Adherence to Medications Using Health Psychology Theories: A Systematic Review of 20 Years of Empirical Research. Value Heal. 2014;17(8):863–76.
              • 39. Rotter JB. Generalized expectancies for internal versus external control of reinforcement. Psychol Monogr. 1966;80(1):1. pmid:5340840
              • 40. Wallston KA, Wallston BS, DeVellis R. Development of the multidimensional health locus of control (MHLC) scales. Heal Educ Behav. 1978;6(1):160–70.
              • 41. Wallston KA, Malcarne VL, Flores L, Hansdottir I, Smith CA, Stein MJ, et al. Does God determine your health? The God locus of health control scale. Cognit Ther Res. 1999;23(2):131–42.
              • 42. Rotter JB, Hochreich DJ. Personality. Glenview, IL: Scott. Foresman, 1975.
                • 43. Wallston KA, Wallston BS. Who is responsible for your health. In: eds. The construct of health locus of control in social psychology of health and illness. City: Lawrence Erlbaum Hillsdale, NJ; 1982. 65–95.
                  • 44. Wallston KA. The importance of placing measures of health locus of control beliefs in a theoretical context. Health Educ Res. 1991;6(2):251–2.
                  • 45. Wallston . The Validity of the Multidimensional Health Locus of Control Scales. J Health Psychol. 2005;10(5):623–31. pmid:16033784
                  • 46. Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gøtzsche PC, Ioannidis JP a, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. J Clin Epidemiol. 2009;62:e1–34. pmid:19631507
                  • 47. Wallace A, Croucher K, Bevan M, Jackson K, O’Malley L, Quilgars D. Evidence for policy making: some reflections on the application of systematic reviews to housing research. Hous Stud. 2006;21(2):297–314.
                  • 48. Neuendorf KA. The content analysis guidebook. London: Sage; 2002.
                    • 49. Lipsey MW, Wilson DB. Practical meta-analysis. Thousand Oaks, CA: Sage; 2001.
                      • 50. Nguyen T-M-U, Caze A La, Cottrell N. What are validated self-report adherence scales really measuring?: a systematic review. Br J Clin Pharmacol. 2014;77:427–45. pmid:23803249
                      • 51. Ogedegbe G, Mancuso CA, Allegrante JP, Charlson ME. Development and evaluation of a medication adherence self-efficacy scale in hypertensive African-American patients. J Clin Epidemiol. 2003;56(6):520–9. pmid:12873646
                      • 52. Arnsten JH, Li X, Mizuno Y, Knowlton AR, Gourevitch MN, Handley K, et al. Factors associated with antiretroviral therapy adherence and medication errors among HIV-infected injection drug users. J Acquir Immune Defic Syndr. 2007;46 Suppl 2:S64–71.
                      • 53. Atkinson JS, Schönnesson LN, Williams ML, Timpson SC. Associations among correlates of schedule adherence to antiretroviral therapy (ART): a path analysis of a sample of crack cocaine using sexually active African-Americans with HIV infection. AIDS Care. 2008;20:253–62. pmid:18293137
                      • 54. Begley K, McLaws M-L, Ross MW, Gold J. Cognitive and behavioural correlates of non-adherence to HIV anti-retroviral therapy: Theoretical and practical insight for clinical psychology and health psychology. Clin Psychol. 2008;12(1):9–17.
                      • 55. Breaux-Shropshire TL, Brown KC, Pryor ER, Maples EH. Relationship of blood pressure self-monitoring, medication adherence, self-efficacy, stage of change, and blood pressure control among municipal workers with hypertension. Workplace Health Saf. 2012;60(7):303–11. pmid:22767462
                      • 56. Brown JL, Littlewood RA, Vanable PA. Social-cognitive correlates of antiretroviral therapy adherence among HIV-infected individuals receiving infectious disease care in a medium-sized northeastern US city. AIDS Care. 2013;25(9):1149–58. pmid:23311323
                      • 57. Brus H, Van De Laar M, Taal E, Rasker J, Wiegman O. Determinants of compliance with medication in patients with rheumatoid arthritis: The importance of self-efficacy expectations. Patient Educ Couns. 1999;36:57–64. pmid:10036560
                      • 58. Burra TA, Chen E, McIntyre RS, Grace SL, Blackmore ER, Stewart DE. Predictors of self-reported antidepressant adherence. Behav Med. 2007;32:127–34. pmid:17348428
                      • 59. Catz SL, Kelly JA, Bogart LM, Benotsch EG, McAuliffe TL. Patterns, correlates, and barriers to medication adherence among persons prescribed new treatments for HIV disease. Health Psychol. 2000;19(2):124–33. pmid:10762096
                      • 60. Chao J, Nau DP, Aikens JE, Taylor SD. The mediating role of health beliefs in the relationship between depressive symptoms and medication adherence in persons with diabetes. Res Soc Adm Pharm. 2005;1:508–25.
                      • 61. Chesney MA, Ickovics JR, Chambers DB, Gifford AL, Neidig J, Zwickl B, et al. Self-reported adherence to antiretroviral medications among participants in HIV clinical trials: the AACTG adherence instruments. AIDS Care. 2000;12(3):255–66. pmid:10928201
                      • 62. Colbert AM, Sereika SM, Erlen JA. Functional health literacy, medication-taking self-efficacy and adherence to antiretroviral therapy. J Adv Nurs. 2013;69:295–304. pmid:22489684
                      • 63. Cook PF, Emiliozzi S, El-Hajj D, McCabe MM. Telephone nurse counseling for medication adherence in ulcerative colitis: A preliminary study. Patient Educ Couns. 2010;81(2):182–6. pmid:20079598
                      • 64. Cook PF, McCabe MM, Emiliozzi S, Pointer L. Telephone Nurse Counseling Improves HIV Medication Adherence: An Effectiveness Study. J Assoc Nurses AIDS Care. 2009;20(4):316–25. pmid:19576548
                      • 65. Criswell TJ, Weber CA, Xu Y, Carter BL. Effect of self‐efficacy and social support on adherence to antihypertensive drugs. Pharmacotherapy. 2010;30(5):432–41. pmid:20411995
                      • 66. Denhaerynck K, Abraham I, Gourley G, Drent G, Vleeschouwer P De, Papajcik D, et al. Validity testing of the long-term medication behavior self-efficacy scale. J Nurs Meas. 2003;11(3):267–82. pmid:15633781
                      • 67. Elder K, Ramamonjiarivelo Z, Wiltshire J, Piper C, Horn WS, Gilbert KL, et al. Trust, medication adherence, and hypertension control in Southern African American men. Am J Public Health. 2012;102(12):2242–5. pmid:22698017
                      • 68. Fransen G a J, Mesters I, Janssen MJR, Knottnerus JA, Muris JWM. Which patient-related factors determine self-perceived patient adherence to prescribed dyspepsia medication? Health Educ Res. 2009;24(5):788–98. pmid:19304927
                      • 69. Fuertes JN, Boylan LS, Fontanella J a. Behavioral indices in medical care outcome: The working alliance, adherence, and related factors. J Gen Intern Med. 2009;24:80–5. pmid:18972089
                      • 70. Gatti ME, Jacgbson KL, Gazmararian J a., Schmotzer B, Kripalani S. Relationships between beliefs about medications and adherence. Am J Heal Pharm. 2009;66:657–64.
                      • 71. Godin G, Côté J, Naccache H, Lambert LD, Trottier S. Prediction of adherence to antiretroviral therapy: a one-year longitudinal study. AIDS Care. 2005;17(May):493–504.
                      • 72. Halkitis PN, Kutnick AH, Slater S. The social realities of adherence to protease inhibitor regimens: substance use, health care and psychological states. J Health Psychol. 2005;10:545–58. pmid:16014391
                      • 73. Johnson MO, Neilands TB, Dilworth SE, Morin SF, Remien RH, Chesney MA. The role of self-efficacy in HIV treatment adherence: Validation of the HIV Treatment Adherence Self-Efficacy Scale (HIV-ASES). J Behav Med. 2007;30:359–70. pmid:17588200
                      • 74. Johnson MO, Catz SL, Remien RH, Rotheram-Borus MJ, Morin SF, Charlebois E, et al. Theory-guided, empirically supported avenues for intervention on HIV medication nonadherence: findings from the Healthy Living Project. AIDS Patient Care STDS. 2003;17(12):645–56. pmid:14746658
                      • 75. Kalichman SC, Rompa D, DiFonzo K, Simpson D, Austin J, Luke W, et al. HIV treatment adherence in women living with HIV/AIDS: research based on the Information-Motivation-Behavioral Skills model of health behavior. J Assoc Nurses AIDS Care. 2001;12(4):58–67. pmid:11486721
                      • 76. Kalichman SC, Kalichman MO, Cherry C, Swetzes C, Amaral CM, White D, et al. Brief behavioral self-regulation counseling for HIV treatment adherence delivered by cell phone: an initial test of concept trial. AIDS Patient Care STDS. 2011;25(5):303–10. pmid:21457056
                      • 77. Kerr T, Marshall A, Walsh J, Palepu A, Tyndall M, Montaner J, et al. Determinants of HAART discontinuation among injection drug users. AIDS Care. 2005;17(July):539–49.
                      • 78. Lewis LM, Schoenthaler AM, Ogedegbe G. Patient Factors, But Not Provider and Health Care System Factors, Predict Medication Adherence in Hypertensive Black Men. J Clin Hypertens. 2012;14(4):250–5.
                      • 79. Mishali M, Omer H, Heymann a. D. The importance of measuring self-efficacy in patients with diabetes. Fam Pract. 2011;28(November 2010):82–7. pmid:21047940
                      • 80. Mo PKH, Mak WWS. Intentionality of medication non-adherence among individuals living with HIV/AIDS in Hong Kong. AIDS Care. 2009;21(6):785–95. pmid:19806492
                      • 81. Molassiotis A, Nahas-Lopez V, Chung WY, Lam SW, Li CK, Lau TF. Factors associated with adherence to antiretroviral medication in HIV-infected patients. Int J STD AIDS. 2002;13(5):301–10. pmid:11972933
                      • 82. Murphy DA, Greenwell L, Hoffman D. Factors associated with antiretroviral adherence among HIV-infected women with children. Women Health. 2002;36(1):97–111. pmid:12215006
                      • 83. Naar-King S, Wright K, Parsons JT, Frey M, Templin T, Lam P, et al. Healthy choices: motivational enhancement therapy for health risk behaviors in HIV-positive youth. AIDS Educ Prev. 2006;18(1):1–11. pmid:16539572
                      • 84. Nokes K, Johnson MO, Webel A, Rose CD, Phillips JC, Sullivan K, et al. Focus on Increasing Treatment Self-Efficacy to Improve Human Immunodeficiency Virus Treatment Adherence. J Nurs Scholarsh. 2012;44:403–10. pmid:23121723
                      • 85. Parsons JT, Rosof E, Mustanski B. Medication adherence mediates the relationship between adherence self-efficacy and biological assessments of HIV health among those with alcohol use disorders. AIDS Behav. 2008;12:95–103. pmid:17503172
                      • 86. Pinheiro CAT, de-Carvalho-Leite JC, Drachler ML, Silveira VL. Factors associated with adherence to antiretroviral therapy in HIV/AIDS patients: a cross-sectional study in Southern Brazil. Brazilian J Med Biol Res. 2002;35(10):1173–81.
                      • 87. Remien RH, Bastos FI, Jnr VT, Raxach JC, Pinto RM, Parker RG, et al. Adherence to antiretroviral therapy in a context of universal access in Rio de Janeiro, Brazil. AIDS Care. 2007;19(6):740–8. pmid:17573593
                      • 88. Resnick B, Wehren L, Orwig D. Reliability and validity of the self-efficacy and outcome expectations for osteoporosis medication adherence scales. Orthop Nurs. 2003;22(2):139–47. pmid:12703398
                      • 89. Safren SA, W. Otto M, Worth JL, Salomon E, Johnson W, Mayer K, et al. Two strategies to increase adherence to HIV antiretroviral medication: Life-Steps and medication monitoring. Behav Res Ther. 2001;39(10):1151–62. pmid:11579986
                      • 90. Schousboe JT, Dowd BE, Davison ML, Kane RL. Association of medication attitudes with non-persistence and non-compliance with medication to prevent fractures. Osteoporos Int. 2010;21:1899–909. pmid:19967337
                      • 91. Shon KH, Park SS. Medication and symptom management education program for the rehabilitation of psychiatric patients in Korea: the effects of promoting schedule on self-efficacy theory. Yonsei Med J. 2002;43(5):579–89. pmid:12402370
                      • 92. Simoni JM, Frick PA, Huang B. A longitudinal evaluation of a social support model of medication adherence among HIV-positive men and women on antiretroviral therapy. Health Psychol. 2006;25(1):74–81. pmid:16448300
                      • 93. Unni E, Farris KB. Determinants of different types of medication non-adherence in cholesterol lowering and asthma maintenance medications: A theoretical approach. Patient Educ Couns. 2011;83(3):382–90. pmid:21454030
                      • 94. Wilson KJ, Doxanakis A, Fairley CK. Predictors for non-adherence to antiretroviral therapy. Sex Health. 2005;1(4):251–7.
                      • 95. Wolf MS, Davis TC, Osborn CY, Skripkauskas S, Bennett CL, Makoul G. Literacy, self-efficacy, and HIV medication adherence. Patient Educ Couns. 2007;65:253–60. pmid:17118617
                      • 96. Archiopoli A, Ginossar T, Wilcox B, Avila M, Hill R, Oetzel J. Factors of interpersonal communication and behavioral health on medication self-efficacy and medication adherence. AIDS Care. 2016;28(12):1607–14. pmid:27320778
                      • 97. Chang Y-P, Compton P, Almeter P, Fox CH. The effect of motivational interviewing on prescription opioid adherence among older adults with chronic pain. Perspect Psychiatr Care. 2015;51(3):211–9. pmid:25159493
                      • 98. Dewing S, Mathews C, Lurie M, Kagee A, Padayachee T, Lombard C. Predictors of poor adherence among people on antiretroviral treatment in Cape Town, South Africa: a case-control study. AIDS Care. 2015;27(3):342–9. pmid:25559444
                      • 99. MacDonell KK, Jacques-Tiura AJ, Naar S, Fernandez MI, Team ATN 086/106 P. Predictors of self-reported adherence to antiretroviral medication in a multisite study of ethnic and racial minority HIV-positive youth. J Pediatr Psychol. 2015;41(4):419–28. pmid:26498724
                      • 100. Náfrádi L, Galimberti E, Nakamoto K, Schulz PJ. Intentional and unintentional medication non-adherence in hypertension: the role of health literacy, empowerment and medication beliefs. J Public Health Res. 2016;5(3): 762. pmid:28083523
                      • 101. Bolman C, Arwert TG, Völlink T. Adherence to prophylactic asthma medication: Habit strength and cognitions. Hear Lung J Acute Crit Care. 2011;40:63–75.
                      • 102. Carpenter DM, DeVellis RF, Fisher EB, DeVellis BM, Hogan SL, Jordan JM. The effect of conflicting medication information and physician support on medication adherence for chronically ill patients. Patient Educ Couns. 2010;81(2):169–76. pmid:20044230
                      • 103. Cha E, Erlen JA, Kim KH, Sereika SM, Caruthers D. Mediating roles of medication-taking self-efficacy and depressive symptoms on self-reported medication adherence in persons with HIV: A questionnaire survey. Int J Nurs Stud. 2008;45:1175–84. pmid:17949723
                      • 104. DiIorio C, McCarty F, DePadilla L, Resnicow K, Holstad MM, Yeager K, et al. Adherence to antiretroviral medication regimens: a test of a psychosocial model. AIDS Behav. 2009;13(1):10–22. pmid:17978868
                      • 105. Gifford AL, Bormann JE, Shively MJ, Wright BC, Richman DD, Bozzette SA. Predictors of self-reported adherence and plasma HIV concentrations in patients on multidrug antiretroviral regimens. JAIDS J Acquir Immune Defic Syndr. 2000;23(5):386–95. pmid:10866231
                      • 106. Marc LG, Testa MA, Walker AM, Robbins GK, Shafer RW, Anderson NB, et al. Educational attainment and response to HAART during initial therapy for HIV-1 infection. J Psychosom Res. 2007;63:207–16. pmid:17662759
                      • 107. Pepper JK, Carpenter DM, De Vellis RF. Does adherence-related support from physicians and partners predict medication adherence for vasculitis patients? J Behav Med. 2012;35:115–23. pmid:22350097
                      • 108. Schoenthaler A, Ogedegbe G, Allegrante JP. Self-efficacy mediates the relationship between depressive symptoms and medication adherence among hypertensive African Americans. Health Educ Behav. 2009;36:127–37. pmid:18077654
                      • 109. Sevelius JM, Carrico A, Johnson MO. Antiretroviral Therapy Adherence Among Transgender Women Living With HIV. J Assoc Nurses AIDS Care. 2010;21(3):256–64. pmid:20347342
                      • 110. Simoni JM, Frick P a, Lockhart D, Liebovitz D. Mediators of social support and antiretroviral adherence among an indigent population in New York City. AIDS Patient Care STDS. 2002;16(9):431–9. pmid:12396695
                      • 111. Bogart LM, Gray-Bernhardt ML, Catz SL, Hartmann BR, Otto-Salaj LL. Social and temporal comparisons made by individuals living with HIV disease: Relationships to adherence behavior. J Appl Soc Psychol. 2002;32:1551–76.
                      • 112. Edworthy SM, Domazei N, Talavera R, Devins GM. Illness intrusiveness: An intervening factor between symptoms and quality of life in patients with systemic lupus erythematosus. Arthritis and Rheumatism. 1998. S221–S221.
                      • 113. Johnson MO, Chesney M a, Goldstein RB, Remien RH, Catz S, Gore-Felton C, et al. Positive provider interactions, adherence self-efficacy, and adherence to antiretroviral medications among HIV-infected adults: A mediation model. AIDS Patient Care STDS. 2006;20(4):258–68. pmid:16623624
                      • 114. Bennett P, Rowe A, Katz D. Reported adherence with preventive asthma medication: a test of protection motivation theory. Psychol Health Med. 1998;3(4):347–54.
                      • 115. Bosma OH, Vermeulen KM, Verschuuren E a., Erasmus ME, Van Der Bij W. Adherence to immunosuppression in adult lung transplant recipients: Prevalence and risk factors. J Hear Lung Transplant. 2011;30(11):1275–80.
                      • 116. Russell CL, Cetingok M, Hamburger KQ, Owens S, Thompson D, Hathaway D, et al. Medication adherence in older renal transplant recipients. Clin Nurs Res. 2010;19:95–112. pmid:20185804
                      • 117. Samal L, Saha S, Chander G, Korthuis PT, Sharma RK, Sharp V, et al. Internet health information seeking behavior and antiretroviral adherence in persons living with HIV/AIDS. AIDS Patient Care STDS. 2011;25(7):445–9. pmid:21682586
                      • 118. Clark NM, Dodge J a. Exploring self-efficacy as a predictor of disease management. Health Educ Behav. 1999;26:72–89. pmid:9952053
                      • 119. Warren-Findlow J, Seymour RB, Shenk D. Intergenerational transmission of chronic illness self-care: Results from the caring for hypertension in African American families study. Gerontologist. 2011;51(1):64–75. pmid:20864590
                      • 120. Anderson KO, Dowds BN, Pelletz RE, Edwards WT, Peeters-Asdourian C. Development and initial validation of a scale to measure self-efficacy beliefs in patients with chronic pain. Pain. 1995;63(1):77–83. pmid:8577493
                      • 121. Kobau R, DiIorio C. Epilepsy self-management: a comparison of self-efficacy and outcome expectancy for medication adherence and lifestyle behaviors among people with epilepsy. Epilepsy Behav. 2003;4(3):217–25. pmid:12791322
                      • 122. Gastal DA, Pinheiro RT, Vazquez DP. Self-efficacy scale for Brazilians with type 1 diabetes. Sao Paulo Med J. 2007;125(2):96–101. pmid:17625707
                      • 123. Chen HF, Tsai YF, Lin YP, Shih MS, Chen JC. The relationships among medicine symptom distress, self-efficacy, patient-provider relationship, and medication compliance in patients with epilepsy. Epilepsy Behav. 2010;19(1):43–9. pmid:20719572
                      • 124. Chen S-Y, Sheu S, Chang C-S, Wang T-H, Huang M-S. The effects of the self-efficacy method on adult asthmatic patient self-care behavior. J Nurs Res. 2010;18(4):266–74. pmid:21139446
                      • 125. Fraser C, Hadjimichael O, Vollmer T. Predictors of Adherence to Copaxone Therapy in Individuals with Relapsing-Remitting Multiple Sclerosis. J Neurosci Nurs. 2001;33(5):231–9. pmid:11668881
                      • 126. Fraser C, Hadjimichael O, Vollmer T. Predictors of Adherence to Glatiramer Acetate Therapy in Individuals with Self-Reported Progressive Forms of Multiple Sclerosis. J Neurosci Nurs. 2003;35(3):163–70. pmid:12830664
                      • 127. Fraser C, Morgante L, Hadjimichael O, Vollmer T. A Prospective Study of Adherence to Glatiramer Acetate in Individuals with Multiple Sclerosis. J Neurosci Nurs. 2004;36(3):120&hyhen. pmid:15233411
                      • 128. Heckman BD, Ellis G. Preventive medication adherence in African American and Caucasian headache patients. Headache. 2011;51:520–32. pmid:21457237
                      • 129. Khdour MR, Hawwa AF, Kidney JC, Smyth BM, McElnay JC. Potential risk factors for medication non-adherence in patients with chronic obstructive pulmonary disease (COPD). Eur J Clin Pharmacol. 2012;68:1365–73. pmid:22476392
                      • 130. Kim JH, Kim GS, Kim EJ, Park S, Chung N, Chu SH. Factors affecting medication adherence and anticoagulation control in Korean patients taking warfarin. J Cardiovasc Nurs. 2011;26(6):466–74. pmid:21912274
                      • 131. Li X, Huang L, Wang H, Fennie KP, He G, Williams AB. Stigma Mediates the Relationship Between Self-Efficacy, Medication Adherence, and Quality of Life Among People Living with HIV/AIDS in China. AIDS Patient Care STDS. 2011;25(11):665–71. pmid:22023316
                      • 132. Mohr DC, Boudewyn a C, Likosky W, Levine E, Goodkin DE. Injectable medication for the treatment of multiple sclerosis: the influence of self-efficacy expectations and injection anxiety on adherence and ability to self-inject. Ann Behav Med. 2001;23:125–32. pmid:11394554
                      • 133. Molloy GJ, Randall G, Wikman A, Perkins-Porras L, Messerli-Burgy N, Steptoe A. Type D personality, self-efficacy, and medication adherence following an acute coronary syndrome. Psychosom Med. 2012;74(1):100–6. pmid:22155940
                      • 134. Morasco BJ, Turk DC, Donovan DM, Dobscha SK. Risk for prescription opioid misuse among patients with a history of substance use disorder. Drug Alcohol Depend. 2013;127(1–3):193–9. pmid:22818513
                      • 135. Scherer YK, Bruce S. Knowledge, attitudes, and self-efficacy and compliance with medical regimen, number of emergency department visits, and hospitalizations in adults with asthma. Hear Lung J Acute Crit Care. 2001;30(August):250–7.
                      • 136. Warren-Findlow J, Seymour RB, Huber LRB. The association between self-efficacy and hypertension self-care activities among African American adults. J Community Health. 2012;37:15–24. pmid:21547409
                      • 137. Sarkar U, Fisher L, Schillinger D. Is self-efficacy associated with diabetes self-management across race/ethnicity and health literacy? Diabetes Care. 2006 Apr;29(4):823–9. pmid:16567822
                      • 138. Yu ZL, Yeoh LY, Seow YY, Luo XC, Griva K. Evaluation of adherence and depression among patients on peritoneal dialysis. Singapore Med J. 2012;53(May 2010):474–80. pmid:22815017
                      • 139. Zwibel H, Pardo G, Smith S, Denney D, Oleen-Burkey M. A multicenter study of the predictors of adherence to self-injected glatiramer acetate for treatment of relapsing-remitting multiple sclerosis. J Neurol. 2011;258:402–11. pmid:20922405
                      • 140. Corless IB, Wantland D, Kirksey KM, Nicholas PK, Human S, Arudo J, et al. Exploring the Contribution of General Self-Efficacy to the Use of Self-Care Symptom Management Strategies by People Living with HIV Infection. AIDS Patient Care STDS. 2012;26(6):335–43. pmid:22612448
                      • 141. Luszczynska A, Sarkar Y, Knoll N. Received social support, self-efficacy, and finding benefits in disease as predictors of physical functioning and adherence to antiretroviral therapy. Patient Educ Couns. 2007;66(1):37–42. pmid:17097259
                      • 142. Ponieman D, Wisnivesky JP, Leventhal H, Musumeci-Szabó TJ, Halm EA. Impact of positive and negative beliefs about inhaled corticosteroids on adherence in inner-city asthmatic patients. Ann Allergy, Asthma Immunol. 2009;103(1):38–42.
                      • 143. Mann DM, Ponieman D, Leventhal H, Halm EA. Predictors of adherence to diabetes medications: the role of disease and medication beliefs. J Behav Med. 2009;32(3):278–84. pmid:19184390
                      • 144. de Guzman AB, Guevara KIJ, Guiang FJB, Gutierrez ALI, Habaluyas AS, Hizon MAP, et al. Developing a Model of Medication Adherence among Filipino Elderly. Educ Gerontol. 2013;39(5):298–313.
                      • 145. Valeberg BT, Miaskowski C, Hanestad BR, Bjordal K, Moum T, Rustøen T. Prevalence rates for and predictors of self-reported adherence of oncology outpatients with analgesic medications. Clin J Pain. 2008;24(7):627–36. pmid:18716502
                      • 146. Mann DM, Ponieman D, Leventhal H, Halm EA. Predictors of adherence to diabetes medications: The role of disease and medication beliefs. J Behav Med. 2009;32:278–84. pmid:19184390
                      • 147. Liu Y, Malin JL, Diamant AL, Thind A, Maly RC. Adherence to adjuvant hormone therapy in low-income women with breast cancer: The role of provider-patient communication. Breast Cancer Res Treat. 2013;137:829–36. pmid:23263740
                      • 148. Curtin RB, Walters BAJ, Schatell D, Pennell P, Wise M, Klicko K. Self-efficacy and self-management behaviors in patients with chronic kidney disease. Adv Chronic Kidney Dis. 2008;15(2):191–205. pmid:18334246
                      • 149. Kamau TM, Olson VG, Zipp GP, Clark M. Coping Self-Efficacy as a Predictor of Adherence to Antiretroviral Therapy in Men and Women Living with HIV in Kenya. AIDS Patient Care STDS. 2011;25(9):557–61. pmid:21777140
                      • 150. Robbins RN, D’Aquila E, Morgello S, Byrd D, Remien RH, Mindt MR. Cultural Influences on Antiretroviral Therapy Adherence Among HIV-Infected Puerto Ricans. J Assoc Nurses AIDS Care. 2012;23(6):531–8. pmid:22525858
                      • 151. Shively M, Smith T, Bormann J, Gifford A. Evaluating self-efficacy for HIV disease management skills. AIDS Behav. 2002;6(4).
                      • 152. Wallston BS, Wallston KA, Kaplan GD, Maides SA. Development and validation of the health locus of control (HLC) scale. J Consult Clin Psychol. 1976;44(4):580. pmid:939841
                      • 153. Wallston K a, Stein MJ, Smith C a. Form C of the MHLC scales: a condition-specific measure of locus of control. J Pers Assess. 1994;63(3):534–53. pmid:7844739
                      • 154. Davis DP, Jandrisevits MD, Iles S, Weber TR, Gallo LC. Demographic, Socioeconomic, and Psychological Factors Related to Medication Non-adherence among Emergency Department Patients. J Emerg Med. 2009;43(5):773–85. pmid:19464136
                      • 155. Halimi L, Vachier I, Varrin M, Godard P, Pithon G, Chanez P. Interference of psychological factors in difficult-to-control asthma. Respir Med. 2007;101:154–61. pmid:16857356
                      • 156. Halimi L, Pry R, Pithon G, Godard P, Varrin M, Chanez P. Severe asthma and adherence to peak flow monitoring: longitudinal assessment of psychological aspects. J Psychosom Res. 2010;69(4):331–40. pmid:20846534
                      • 157. Fransen G a J, Mesters I, Janssen MJR, Knottnerus J a., Muris JWM. Which patient-related factors determine self-perceived patient adherence to prescribed dyspepsia medication? Health Educ Res. 2009;24:788–98. pmid:19304927
                      • 158. Kaya Z, Erkan F, Ozkan M, Ozkan S, Kocaman N, Ertekin BA, et al. Self-management plans for asthma control and predictors of patient compliance. J Asthma. 2009;46:270–5. pmid:19373635
                      • 159. Wang PS, Bohn RL, Knight E, Glynn RJ, Mogun H, Avorn J. Noncompliance with antihypertensive medications: The impact of depressive symptoms and psychosocial factors. J Gen Intern Med. 2002;17:504–11. pmid:12133140
                      • 160. Cotton S, Antill JK. Noncompliance: medical and psychological aspects. Aust Psychol. 1984;19(2):193–204.
                      • 161. Holloway RL, Rogers JC, Gershenhorn SL. Differences between patient and physician perceptions of predicted compliance. Fam Pract. 1992;9(3):318–22. pmid:1459389
                      • 162. Katerndahl DA. Locus of control and field dependence in prediction. J Nerv Ment Dis. 2001;189(5):335–8. pmid:11379981
                      • 163. Barclay TR, Hinkin CH, Castellon SA, Mason KI, Reinhard MJ, Marion SD, et al. Age-associated predictors of medication adherence in HIV-positive adults: health beliefs, self-efficacy, and neurocognitive status. Health Psychol. 2007;26(1):40–9. pmid:17209696
                      • 164. Bazargan M, Barbre AR, Hamm V. Failure to have prescriptions filled among Black elderly. J Aging Health. 1993;5(2):264–82. pmid:10125448
                      • 165. Darling CA, Olmstead SB, Lund VE, Fairclough JF. Bipolar Disorder: Medication Adherence and Life Contentment. Arch Psychiatr Nurs. 2008;22(3):113–26. pmid:18505693
                      • 166. Hong TB, Oddone EZ, Dudley TK, Bosworth HB. Medication barriers and anti-hypertensive medication adherence: the moderating role of locus of control. Psychol Health Med. 2006;11(1):20–8. pmid:17129892
                      • 167. O’Hea EL, Grothe KB, Bodenlos JS, Boudreaux ED, White M a, Brantley PJ. Predicting medical regimen adherence: the interactions of health locus of control beliefs. J Health Psychol. 2005;10:705–17. pmid:16033792
                      • 168. Stanton AL. Determinants of adherence to medical regimens by hypertensive patients. J Behav Med. 1987;10(4):377–94. pmid:3669072
                      • 169. Theofilou P. Medication adherence in Greek hemodialysis patients: The contribution of depression and health cognitions. Int J Behav Med. 2013;20:311–8. pmid:22407452
                      • 170. Wulandari LPL, Craig P, Whelan AK. Foetal Health Locus of Control and iron supplementation adherence among pregnant women in Bali. J Reprod Infant Psychol. 2013;31(1):94–101.
                      • 171. Raiz LR, Kilty KM, Henry ML, Ferguson RM. Medication compliance following renal transplantation. Transplantation. 1999;68(1):51–5. pmid:10428266
                      • 172. Ahmedani BK, Peterson EL, Wells KE, Rand CS, Williams LK. Asthma medication adherence: the role of God and other health locus of control factors. Ann Allergy. 2013;110(2):75–79. e2.
                      • 173. Altice FL, Mostashari F, Friedland GH. Trust and the acceptance of and adherence to antiretroviral therapy. J Acquir Immune Defic Syndr. 2001;28(1):47–58. pmid:11579277
                      • 174. Apter AJ, Reisine ST, Affleck G, Barrows E, ZuWallack RL. Adherence with twice-daily dosing of inhaled steroids: Socioeconomic and health-belief differences. Am J Respir Crit Care Med. 1998;157:1810–7. pmid:9620910
                      • 175. Bane C, Hughes CM, McElnay JC. The impact of depressive symptoms and psychosocial factors on medication adherence in cardiovascular disease. Patient Educ Couns. 2006;60:187–93. pmid:16253468
                      • 176. Budd RJ, Hughes ICT, Smith JA. Health beliefs and compliance with antipsychotic medication. Br J Clin Psychol. 1996;35(3):393–7.
                      • 177. Graveley EA, Oseasohn CS. Multiple drug regimens: medication compliance among veterans 65 years and older. Res Nurs Health. 1991;14(1):51–8. pmid:2017581
                      • 178. Hargrave R, Remler MP. Noncompliance. J Natl Med Assoc. 1996;88(1):7, 11. pmid:8583495
                      • 179. Lamba S, Nagurka R, Desai KK, Chun SJ, Holland B, Koneru B. Self-reported non-adherence to immune-suppressant therapy in liver transplant recipients: Demographic, interpersonal, and intrapersonal factors. Clin Transplant. 2012;26(2):328–35. pmid:21955028
                      • 180. Lynam I, Catley D, Goggin K, Rabinowitz JL, Gerkovich MM, Williams K, et al. Autonomous regulation and locus of control as predictors of antiretroviral medication adherence. J Health Psychol. 2009;14:578–86. pmid:19383658
                      • 181. McDonald-Miszczak L, Maki SA, Gould ON. Self-reported medication adherence and health status in late adulthood: The role of beliefs. Exp Aging Res. 2000;26(3):189–207. pmid:10919066
                      • 182. McDonough EM, Boyd JH, Varvares MA, Maves MD. Relationship between psychological status and compliance in a sample of patients treated for cancer of the head and neck. Head Neck. 1996;18(3):269–76. pmid:8860769
                      • 183. Reach G, Michault a., Bihan H, Paulino C, Cohen R, Le Clésiau H. Patients’ impatience is an independent determinant of poor diabetes control. Diabetes Metab. 2011;37(6):497–504. pmid:21550831
                      • 184. Weng FL, Israni AK, Joffe MM, Hoy T, Gaughan CA, Newman M, et al. Race and electronically measured adherence to immunosuppressive medications after deceased donor renal transplantation. J Am Soc Nephrol. 2005;16(6):1839–48. pmid:15800121
                      • 185. Williams GC, Rodin GC, Ryan RM, Grolnick WS, Deci EL. Autonomous regulation and long-term medication adherence in adult outpatients. Health Psychol. 1998;17(3):269–76. pmid:9619477
                      • 186. Craig H, Wright B. Nonadherence to prophylactic medication: Negative attitudes toward doctors a strong predictor. Aust Fam Physician. 2012;41(10):815. pmid:23210108
                      • 187. Kamolz T. Analysis of medical compliance in gastro-oesophageal reflux disease patients referred to pre-surgical examination. Dig Liver Dis. 2002;34:183–9. pmid:11990390
                      • 188. Frazier PA, Davis-Ali SH, Dahl KE. Correlates of noncompliance among renal transplant recipients. Clin Transplant. 1994;8(6):550–7. pmid:7865918
                      • 189. Abbott J, Dodd M, Webb a K. Health perceptions and treatment adherence in adults with cystic fibrosis. Thorax. 1996;51:1233–8. pmid:8994521
                      • 190. Weng FL, Israni AK, Joffe MM, Hoy T, Gaughan C a, Newman M, et al. Race and electronically measured adherence to immunosuppressive medications after deceased donor renal transplantation. J Am Soc Nephrol. 2005;16(19):1839–48.
                      • 191. Aversa SL, Kimberlin C. Psychosocial aspects of antiretroviral medication use among HIV patients. Patient Educ Couns. Elsevier; 1996;29(2):207–19. pmid:9006237
                      • 192. Sajatovic M, Ignacio R V., West J a., Cassidy K a., Safavi R, Kilbourne AM, et al. Predictors of nonadherence among individuals with bipolar disorder receiving treatment in a community mental health clinic. Compr Psychiatry. 2009;50(2):100–7. pmid:19216885
                      • 193. Schneider B. Multidimensional health locus of control as partial predictor of serum phosphorus in chronic hemodialysis. Psychol Rep. 1992;70(3 Pt 2):1171–4.
                      • 194. Myers LB, Myers F. The relationship between control beliefs and self-reported adherence in adults with cystic fibrosis. Psychol Health Med. 1999;4(4):387–91.
                      • 195. Sajatovic M, Micula-Gondek W, Tatsuoka C, Bialko C. The relationship of gender and gender identity to treatment adherence among individuals with bipolar disorder. Gend Med. 2011;8(4):261–8. pmid:21763217
                      • 196. Williams GC, Rodin GC, Ryan RM, Grolnick WS, Deci EL. Autonomous regulation and long-term medication adherence in adult outpatients. Heal Psychol. 1998;17(3):269.
                      • 197. Lamba S, Nagurka R, Desai KK, Chun SJ, Holland B, Koneru B. Self‐reported non‐adherence to immune‐suppressant therapy in liver transplant recipients: demographic, interpersonal, and intrapersonal factors. Clin Transplant. 2012;26(2):328–35. pmid:21955028
                      • 198. Berglund E, Lytsy P, Westerling R. Adherence to and beliefs in lipid-lowering medical treatments: A structural equation modeling approach including the necessity-concern framework. Patient Educ Couns. 2013;91(1):105–12. pmid:23218590
                      • 199. Voils CI, Steffens DC, Flint EP, Bosworth HB. Social support and locus of control as predictors of adherence to antidepressant medication in an elderly population. Am J Geriatr Psychiatry. 2005;13:157–65. pmid:15703325
                      • 200. O’Hea EL, Moon S, Grothe KB, Boudreaux E, Bodenlos JS, Wallston K, et al. The interaction of locus of control, self-efficacy, and outcome expectancy in relation to HbA1c in medically underserved individuals with type 2 diabetes. J Behav Med. 2009;32:106–17. pmid:19089606
                      • 201. Christensen AJ, Wiebe JS, Benotsch EG, Lawton WJ. Perceived health competence, health locus of control, and patient adherence in renal dialysis. Cognit Ther Res. 1996;20(4):411–21.
                      • 202. Christensen AJ, Wiebe JS, Lawton WJ. Cynical hostility, powerful others control expectancies, and patient adherence in hemodialysis. Psychosom Med. 1997;59(1):307–12.
                      • 203. Atkins L, Fallowfield L. Intentional and non-intentional non-adherence to medication amongst breast cancer patients. Eur J Cancer. 2006;42(14):2271–6. pmid:16644208
                      • 204. Schneider A, Wensing M, Quinzler R, Bieber C, Szecsenyi J. Higher preference for participation in treatment decisions is associated with lower medication adherence in asthma patients. Patient Educ Couns. 2007;67:57–62. pmid:17346917
                      • 205. Gremigni P, Bacchi F, Turrini C, Cappelli G, Albertazzi A, Bitti PER. Psychological factors associated with medication adherence following renal transplantation. Clin Transplant. 2007;21(4):710–5.
                      • 206. Cholowski K, Cantwell R. Predictors of medication compliance among older heart failure patients. Int J Older People Nurs. 2007;2(4):250–62. pmid:20925839
                      • 207. Kennedy S, Goggin K, Nollen N. Adherence to HIV medications: Utility of the theory of self-determination. Cognit Ther Res. 2004;28(5):611–28.
                      • 208. Molassiotis A, Morris K, Trueman I. The importance of the patient-clinician relationship in adherence to antiretroviral medication. Int J Nurs Pract. 2007;13:370–6. pmid:18021166
                      • 209. Williams GC, Patrick H, Niemiec CP, Williams LK, Divine G, Lafata JE, et al. Reducing the health risks of diabetes: how self-determination theory may help improve medication adherence and quality of life. Diabetes Educ. 2009;35:484–92. pmid:19325022
                      • 210. Peyrot M, Rubin RR. Structure and correlates of diabetes-specific locus of control. Diabetes Care. 1994;17(9):994–1001. pmid:7988321
                      • 211. Stenström CH, Arge B, Sundbom A. Home exercise and compliance in inflammatory rheumatic diseases—a prospective clinical trial. J Rheumatol. 1997;24(3):470–6. pmid:9058651
                      • 212. Cvengros JA, Christensen AJ, Hillis SL, Rosenthal GE. Patient and physician attitudes in the health care context: Attitudinal symmetry predicts patient satisfaction and adherence. Ann Behav Med. 2007;33:262–8. pmid:17600453
                      • 213. Christensen AJ, Howren MB, Hillis SL, Kaboli P, Carter BL, Cvengros JA, et al. Patient and physician beliefs about control over health: Association of symmetrical beliefs with medication regimen adherence. J Gen Intern Med. 2010;25:397–402. pmid:20174972
                      • 214. Ridic G, Gleason S, Ridic O. Comparisons of Health Care Systems in the United States, Germany and Canada. Mater Sociomed. 2012; 24(2): 112–120. pmid:23678317
                      • 215. Schulz PJ, Nakamoto K. Health literacy and patient empowerment in health communication: the importance of separating conjoined twins. Patient Educ Couns. 2013;90(1):4–11. pmid:23063359
                      • 216. Chiu C, Feuz M a., McMahan RD, Miao Y, Sudore RL. “doctor, make my decisions”: Decision control preferences, advance care planning, and satisfaction with communication among diverse older adults. J Pain Symptom Manage. 2016;51(1):33–40. pmid:26342727
                      • 217. Charles C, Gafni A, Whelan T. Decision-making in the physician-patient encounter: Revisiting the shared treatment decision-making model. Soc Sci Med. 1999;49:651–61. pmid:10452420
                      • 218. Náfrádi L, Nakamoto K, Csabai M, Papp-zipernovszky O, Schulz PJ. An empirical test of the Health Empowerment Model : Does patient empowerment moderate the effect of health literacy on health status ? Patient Educ Couns. 2017
                      • 219. Charles C, Gafni A, Whelan T. Shared decision-making in the medical encounter: What does it mean? (Or it takes, at least two to tango). Soc Sci Med. 1997;44(5):681–92. pmid:9032835
                      • 220. Hooper L. Publication bias : what is it ? How do we measure it ? How do we avoid it ? Open Access Journal of Clinical Trials. 2013; 5:71–81.