The association of depression with adherence to antihypertensive medications: a systematic review

Abstract

Objective-To examine the strength and consistency of the evidence on the relationship between depression and adherence to antihypertensive medications.Methods-The MEDLINE, CINAHL, PsycINFO, Embase, SCOPUS, and ISI databases were searched from inception until December 11, 2009 for published studies of original research that assessed adherence to antihypertensive medications and used a standardized interview, validated questionnaire or International Classification of Diseases Ninth Revision (ICD-9) code to assess depression or symptoms of depression in patients with hypertension. Manual searching was conducted on 22 selected journals. Citations of included articles were tracked using Web of Science and Google Scholar. Two investigators independently extracted data from the selected articles and discrepancies were resolved by consensus.Results-Eight studies were identified that included a total of 42,790 patients. 95% of these patients were from one study. Only 4 of the studies had the assessment of this relationship as a primary objective. Adherence rates varied from 29% to 91%. There were widely varying results within and across studies. All 8 studies reported at least one significant bivariate or multivariate negative relationship between depression and adherence to antihypertensive medications. Insignificant findings in bivariate or multivariate analyses were reported in 6 of 8 studies.Conclusions-All studies reported statistically significant relationships between depression and poor adherence to antihypertensive medications, but definitive conclusions cannot be drawn because of substantial heterogeneity between studies with respect to the assessment of depression [6,7], optimal blood pressure control is achieved in less than two-thirds of patients who are prescribed antihypertensive treatment [6]. The major modifiable cause of poor control in patients on therapy is nonadherence to antihypertensive medications [8]. Since hypertension generally does not cause symptoms, cues to take medications are often absent. Indeed, "not remembering" to take antihypertensive medications has been shown to be the most common reason for treatment nonadherence [9]. Factors shown to be associated with adherence to antihypertensive treatment include age [10], medication side effects [11,12], race/ethnicity [13,14], and medication cost [15].Depression is present in approximately 5-10% of patients in primary care [16] and is associated with a 3-fold greater risk of nonadherence to medical treatment [17]. Depression therefore represents a potentially important predictor of treatment nonadherence in patients with hypertension. The importance of understanding the relationship between depression and antihypertensive treatment nonadherence is underlined when one considers that depressed patients are at greater risk than those without depression to develop hypertension [18]. This systematic review of the literature was therefore conducted to assess the strength and consistency of evidence linking depression or depressive symptoms...

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