Elsevier

General Hospital Psychiatry

Volume 34, Issue 3, May–June 2012, Pages 249-253
General Hospital Psychiatry

Psychiatric–Medical Comorbidity
The relationship between depressive symptoms and medication nonadherence in type 2 diabetes: the role of social support,☆☆

https://doi.org/10.1016/j.genhosppsych.2012.01.015Get rights and content

Abstract

Objective

Medication adherence promotion interventions are needed that target modifiable behavioral factors contributing to the link between depressive symptoms and poor adherence to diabetes self-care behaviors. In an effort to identify what factors contribute to this link, we examined the role of social support as a mediator of the relationship between depressive symptoms and medication nonadherence.

Method

We recruited 139 subjects with type 2 diabetes. Using an indirect effect test with bias-corrected (BC) bootstrapping, we tested whether depressive symptoms had an indirect effect on medication nonadherence through a lack of social support.

Results

More depressive symptoms were associated with medication nonadherence (total effect=.06, P<.001), more depressive symptoms were associated with less social support (direct effect of the predictor on the mediator=−.96, P=.02), and less social support was associated with medication nonadherence (direct effect of the mediator on the outcome=−.01, P<.01). While the relationship between more depressive symptoms and medication nonadherence persisted with social support in the predicted pathway, the degree of this relationship was partially explained by a relationship between more depressive symptoms and less social support (indirect effect=.01, 95% BC bootstrapped confidence interval of .0005 to .0325).

Conclusion

Providing social support to patients with diabetes who have symptoms of depression may ameliorate some of the deleterious effects of depressive symptoms on medication nonadherence, but social support alone is not enough.

Introduction

Adherence to hypoglycemic agents is important for glycemic control [1], decreases hospitalizations and, in turn, reduces healthcare costs [2]. However, medication adherence is often suboptimal and varies between oral-agent-only (36%–87%) versus concomitant or insulin-only (54%–81%) regimens [2]. There are several barriers to medication adherence, including cost, forgetting, difficulty reading prescription drug labels and obtaining refills [3], and a diagnosis of depression [4].

Diabetes and comorbid depression are associated with poor adherence to self-care behaviors, including medication adherence, as well as a reduction in quality of life, poor metabolic control and an increased risk of mortality [5], [6]. Antidepressant agents effectively minimize depressive symptoms [7], but do not effectively improve diabetes self-care behaviors [8] or glycemic control [7], and adherence to oral hypoglycemic agents may actually get worse over time [8]. Thus, nonpharmacological, medication adherence promotion interventions are needed that target modifiable behavioral factors contributing to the link between depressive symptoms or a clinical diagnosis of depression and poor adherence to hypoglycemic agents.

Medication adherence promotion interventions in other chronic disease contexts (e.g., HIV, hypertension) often target social support (i.e., help patients identify sources of social support networks and/or serve as a source of support for the patient) in an effort to overcome patient deficits in this domain [9], [10]. While there has been mixed evidence regarding a relationship between a lack of social support and medication nonadherence or vice versa (i.e., a relationship between social support and medication adherence), most studies in this literature have found support for this relationship [10], [11], [12], [13]. In contrast, depression is consistently associated with both a lack of social support [14], [15] and medication nonadherence [6], [16], but there is minimal evidence suggesting that the relationship between depression and medication nonadherence persists after adjustment for social support [17]. Further, there is no evidence, to our knowledge, that a lack of social support explains the relationship between depression and medication nonadherence in diabetes or in other chronic health conditions.

Thus, our study objective was to examine the role of social support, or the lack thereof, on the relationship between depressive symptoms and nonadherence to diabetes medications. We specifically tested the hypothesis that the relationship between depressive symptoms and medication nonadherence would be either fully or partially explained by a lack of social support after controlling for relevant covariates. Evidence in support of this hypothesis would imply that providing social support to patients with diabetes and depressive symptoms might counteract the negative effect of these symptoms on medication nonadherence.

Section snippets

Participants

We recruited consecutive patients with diagnosed type 2 diabetes mellitus (T2DM) and scheduled appointments at the internal medicine clinic of an academic medical center in the Southeastern United States. The institutional review board at our institution approved all procedures prior to study enrollment. Eligible participants were clinic patients aged 18 years or older with a diagnosis of T2DM in the medical record and a clinic appointment between June and August 2008. We approached consecutive

Results

A total of 139 participants completed all measures noted above. Mean (S.D.) age was 62.7 (11.9) years. The majority were female (71.9%), were African American (71.4%), were not employed (78.3%), had a high school education or greater (65.9%), had an annual income >$15K (64.2%) and had health insurance (96.4%); 61.9% were categorized as having no depressive symptoms, 23.8% as having mild depressive symptoms and 14.3% as having major depressive symptoms. Sample characteristics by medication

Conclusion

Our findings suggest that more depressive symptoms have an indirect effect on medication nonadherence through a lack of social support (i.e., part of the direct effect of more depressive symptoms on medication nonadherence is due to a relationship between having more depressive symptoms and, in turn, less social support), but social support does explain depression's direct effect on medication nonadherence. Hence, providing social support to patients with diabetes and comorbid depression will

Acknowledgment

Dr. Osborn is supported by a National Institutes of Health (NIH) Career Development Award (NIDDK K01 DK087894). Dr. Egede is supported by an NIH Career Development Award (NIDDK K24 DK093699).

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    Authors' contributions: Study concept and design: Egede and Osborn. Acquisition of data: Egede. Analysis and interpretation of data: Egede and Osborn. Drafting of the manuscript: Osborn. Critical revision of the manuscript for important intellectual content: Egede. Study supervision: Egede.

    ☆☆

    Disclosure: None of the authors disclosed any financial or other conflicts of interest.

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