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OBJECTIVE -- Depression is common in patients with diabetes and is associated with worse treatment outcomes. Its relationship to treatment adherence, however, has not been systematically reviewed. We used meta-analysis to examine the relationship between depression and treatment nonadherence in patients with type 1 and type 2 diabetes. RESEARCH DESIGN AND METHODS -- We searched MEDLINE and PsycINFO databases for all studies published by June 2007 and reviewed references of published articles. Meta-analytic procedures were used to estimate the effect size r in a random effects model. Significance values, weighted effect sizes, 95% CIs, and tests of homogeneity of variance were calculated. RESULTS -- Results from 47 independent samples showed that depression was significantly associated with nonadherence to the diabetes treatment regimen (z = 9.97, P < 0.0001). The weighted effect size was near the medium range (r = 0.21, 95% CI 0.17-0.25). Moderator analyses showed that the effect was significantly larger in studies that measured self-care as a continuous versus categorical variable (P = 0.001). Effect sizes were largest for missed medical appointments and composite measures of self-care (r values = 0.31, 0.29). Moderation analyses suggest that effects for most other types of self-care are also near the medium range, especially in studies with stronger methodologies. CONCLUSIONS-- These findings demonstrate a significant association between depression and treatment nonadherence in patients with diabetes. Studies that used stronger methodologies had larger effects. Treatment nonadherence may represent an important pathway between depression and worse diabetes clinical outcomes. [ABSTRACT FROM AUTHOR]

OBJECTIVE -- We examined the association between depression, measured as either a continuous symptom severity score or a clinical disorder variable, with self-care behaviors in type 2 diabetes. RESEARCH DESIGN AND METHODS -- We surveyed 879 type 2 diabetic patients from two primary care clinics using the Harvard Department of Psychiatry/National Depression Screening Day Scale (HANDS), the Summary of Diabetes Self-Care Activities, and self-reported medication adherence. RESULTS -- Of the patients, 19% met the criteria for probable major depression (HANDS score ±9), and an additional 66.5% reported at least some depressive symptoms. After controlling for covariates, patients with probable major depression reported significantly fewer days' adherent to diet, exercise, and glucose self-monitoring regimens (P < 0.01) and 2.3-fold increased odds of missing medication doses in the previous week (95% CI 1.5-3.6, P < 0.001) compared with all other respondents. Continuous depressive symptom severity scores were better predictors of nonadherence to diet, exercise, and medications than categorically defined probable major depression. Major depression was a better predictor of glucose monitoring. Among the two-thirds of patients not meeting the criteria for major depression (HANDS score < 9, n = 709), increasing HANDS scores were incrementally associated with poorer self-care behaviors (P < 0.01). CONCLUSIONS -- These findings challenge the conceptualization of depression as a categorical risk factor for nonadherence and suggest that even low levels of depressive symptomatology are associated with nonadherence to important aspects of diabetes self-care. Interventions aimed at alleviating depressive symptoms, which are quite common, could result in significant improvements in diabetes self-care. [ABSTRACT FROM AUTHOR]