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