The role of depressive symptoms and self-efficacy in the relationship between activities of daily living and medication adherence among the elderly with chronic diseases: a serial mediation model

The current study aimed to test the effects of depressive symptoms and self-efficacy in the relationship between activities of daily living (ADLs) and medication adherence using a serial mediation model. This cohort study was conducted among 797 elderly with chronic diseases in Hunan Province of China. Their ADLs, medication adherence, self-efficacy, and depressive symptoms were assessed by the Barthel Index (BI), the Morisky Medication Adherence Scale (MMAS-8), the Self-Efficacy for Appropriate Medication Use Scale (SEAMS), and the 20-item Center for Epidemiologic Studies Depression Scale (CES-D), respectively. The PROCESS SPSS Macro version 4.1, model 6, was used to test the serial mediation model of ADLs affecting medication adherence through self-efficacy and depressive symptoms. From baseline to follow-up, the elderly had a significant increase in depressive symptoms (from 15.3 ± 11.3 to 19.1 ± 13.1) and significant decreases in ADLs (from 71.4 ± 19.8 to 64.9 ± 17.61), self-efficacy (from 21.5 ± 5.4 to 20.4 ± 6.2), and medication adherence (from 6.7 ± 1.8 to 6.0 ± 1.5), all with p < 0.001. The serial mediation model demonstrated a robust association between ADLs and medication adherence, which was serially mediated by depressive symptoms and self-efficacy (total effect c = 0.499, 95% CI = 0.393 to 0.605; direct effect c' = 0.379, 95% CI = 0.281 to 0.477; total indirect effect ab = 0.120, 95% CI = 0.073 to 0.168). This study elucidates the association between ADL and medication adherence, clarifying the mediating roles of depressive symptoms and self-efficacy. Our findings suggest that future medication adherence intervention programs among the elderly with chronic illness may be effective by focusing on decreasing depressive symptoms and improving self-efficacy.