Original research
The mediating role of health beliefs in the relationship between depressive symptoms and medication adherence in persons with diabetes

https://doi.org/10.1016/j.sapharm.2005.09.002Get rights and content

Abstract

Background

Although bivariate relationships between depressive symptoms, health beliefs, and medication adherence have been identified, the complex relationship among these 3 constructs has not been explicated.

Objective

This study examines the mediating role of patients' beliefs about diabetes and diabetes medications in relation to depressive symptoms and diabetes medication adherence.

Methods

A survey was sent to 1700 persons with type 2 diabetes who were enrolled in a managed care organization in the United States. The bivariate relationships between depressive symptoms, diabetes-related health beliefs, and diabetes medication adherence were assessed. A structural equation model was developed to determine if health beliefs mediated the relationship between depressive symptoms and medication adherence.

Results

Usable responses were received from 445 subjects. Greater depressive symptoms were associated with lower adherence to diabetes medications. The structural equation model indicated that the effect of depressive symptoms on medication adherence was mediated through perceived side effect barriers, perceived general barriers, and self-efficacy. Patients with severe depressive symptoms perceived more barriers to treatment adherence and were less confident in their ability to adhere to medication. In turn, reduced self-efficacy and heightened perceived barriers had a negative association with patients' adherence to diabetes medication regimens.

Conclusions

Decreased adherence to diabetes medications in patients with both diabetes and depressive symptoms may be partly explained by the association of depression with patients' beliefs about diabetes medications and their self-efficacy for medication use.

Introduction

The United Kingdom Prospective Diabetes Study demonstrated that intensive treatment with medications is one of the most important tools to achieve glycemic control in patients with diabetes.1 However, suboptimal adherence to diabetes medication has been frequently reported in the literature. In a systematic review of studies regarding adherence to diabetes medication regimens, Cramer found that adherence to oral antihyperglycemic regimens ranged from 36% to 93%.2 Nonadherence to diabetes medications is one of the major contributors to poor glycemic control3, 4 and is also associated with a higher cost of medical care.5, 6

Suboptimal adherence to diabetes medication may be associated with several factors including depressive symptoms and one's beliefs about diabetes and diabetes medications. Understanding the impact of depression on diabetes self-care behaviors is important, as a recent meta-analysis showed that major depression and elevated depressive symptoms affected, respectively, 11% and 31% of individuals with diabetes.7 Furthermore, several studies across a range of chronic conditions including diabetes have found that depressive symptoms may be associated with nonadherence to medications.8, 9, 10, 11, 12, 13

Numerous mechanisms for the effect of depression on medication adherence have been proposed. Poor motivation, lack of social support, or a decrease in attention or memory, which all accompany depression, could contribute to nonadherence to medications.9, 11, 14 Depression is also associated with several health beliefs, which, in turn, may affect medication adherence. For example, depression-related pessimism and hopelessness may make it more difficult for patients to perceive treatment benefits and amplify their perceptions of treatment barriers.9 In persons with diabetes, greater depressive symptoms have been associated with higher perceived severity of diabetes, greater perceived susceptibility to diabetes complications, higher perceived barriers to self-care, and lower self-efficacy for diabetes self-care.15, 16, 17 A meta-analysis of adherence studies in diabetes patients also showed that nonadherence to medications was associated with the aforementioned health beliefs.18

Section snippets

Conceptual framework

The conceptual framework for this study was the revised health belief model (HBM) as described by Strecher and Rosenstock.19 As derived from a value-expectancy framework, the HBM reflects that the probability of engaging in a preventive health behavior (eg, medication-taking) is a function of several factors: the perceived threat (comprising one's perceived susceptibility to a health problem and the perceived severity of that problem); the perceived benefits of the health behavior relative to

Subjects

After the study was approved by the University of Michigan Institutional Review Board, a sample was drawn from the members of a managed care organization in the midwestern United States. More than 6000 adults (age ≥18 years) who were likely to have diabetes were identified from medical and pharmacy claims data using the Healthplan Employer Data Information Set technical specifications.22 Based on these specifications, the identified subjects had more than one claim for a diabetes medication as

Sample description

Of the initial mailing to 1700 subjects, 254 questionnaires were undeliverable, resulting in 1446 potential responses. There were 694 usable questionnaires returned, resulting in a net response rate of 48%. After excluding subjects who used insulin, 445 subjects who used oral diabetes medications were included in the analyses. The average age of the oral diabetes medication users was 56.3 years (SD, 11.4 years), with almost equal numbers of females and males (50.1% vs 49.9%). Most of the

Discussion

This study confirmed previous research using bivariate analysis that depressive symptoms were associated with lower diabetes medication adherence upon. However, the structural equation model revealed that the relationship between depressive symptoms and adherence was mediated through perceived general barriers, perceived side effect barriers, and self-efficacy, and to our knowledge, this is the first study to examine this issue. Moreover, the study identified that concerns about medication side

Conclusions

The effect of depressive symptoms on diabetes medication adherence was mediated through perceived general barriers, perceived side effect barriers, and self-efficacy. The findings could benefit the development of strategies to improve the self-management of diabetes. Health care providers should pay attention to the potential role of depressive symptoms in shaping their patients' medication adherence for chronic conditions. In addition to screening diabetes patients for depression, providers

Acknowledgments

This study was funded by the University of Michigan Health System through the Collaborative Health Services Research Initiative (D.P.N., principal investigator). The authors would like to thank MCARE (especially Thom Spafford) for assistance in identifying the sample for the survey. Additionally, the authors thank Duane Kirking and Frank Yates for their helpful comments as well as Tiffany-Jade Sullivan for assistance with data collection.

References (58)

  • S. Genuth et al.

    Implications of the United Kingdom prospective diabetes study

    Diabetes Care

    (2003)
  • J.A. Cramer

    A systematic review of adherence with medications for diabetes

    Diabetes Care

    (2004)
  • D.J. Cox et al.

    Major developments in behavioral diabetes research

    J Consult Clin Psychol

    (1992)
  • K.L. Hepke et al.

    Costs and utilization associated with pharmaceutical adherence in a diabetic population

    Am J Manag Care

    (2004)
  • R.J. Anderson et al.

    The prevalence of comorbid depression in adults with diabetes: a meta-analysis

    Diabetes Care

    (2001)
  • P.S. Ciechanowski et al.

    Depression and diabetes: impact of depressive symptoms on adherence, function, and costs

    Arch Intern Med

    (2000)
  • M.R. DiMatteo et al.

    Depression is a risk factor for noncompliance with medical treatment: meta-analysis of the effects of anxiety and depression on patient adherence

    Arch Intern Med

    (2000)
  • E.H. Lin et al.

    Relationship of depression and diabetes self-care, medication adherence, and preventive care

    Diabetes Care

    (2004)
  • P.S. Wang et al.

    Noncompliance with antihypertensive medications: the impact of depressive symptoms and psychosocial factors

    J Gen Intern Med

    (2002)
  • J.S. Gonzalez et al.

    Social support, positive states of mind, and HIV treatment adherence in men and women living with HIV/AIDS

    Health Psychol

    (2004)
  • K.S. Lewis et al.

    Health belief scales developed specifically for people with tablet-treated type 2 diabetes

    Diabet Med

    (1990)
  • F. Talbot et al.

    The assessment of diabetes-related cognitive and social factors: the Multidimensional Diabetes Questionnaire

    J Behav Med

    (1997)
  • M. Nagasawa et al.

    Meta-analysis of correlates of diabetes patients' compliance with prescribed medications

    Diabetes Educ

    (1990)
  • V.J. Strecher et al.

    The health belief model

  • D.P. Nau et al.

    A perceived value model for explaining patients' intentions to continue use of pharmaceutical care services

    J Pharm Market Manag

    (2001)
  • D.L. Ronis

    Conditional health threats: health beliefs, decisions, and behaviors among adults

    Health Psychol

    (1992)
  • National Committee for Quality Assurance

    HEDIS 2001 Technical Specifications

    (2001)
  • R.E. Glasgow et al.

    Regimen adherence: a problematic construct in diabetes research

    Diabetes Care

    (1985)
  • K.A. Cerkoney et al.

    The relationship between the health belief model and compliance of persons with diabetes mellitus

    Diabetes Care

    (1980)
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    f

    At the time of this study, Drs Chao and Taylor were affiliated with the Department of Social and Administrative Sciences at the University of Michigan College of Pharmacy.

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