The impact of stigma on medication adherence among patients with multimorbidity: mediation analysis of medication literacy

Purpose The relationship among stigma, medication literacy and medication adherence in patients with multimorbidity is limited. This study was to explore the relationships among medication literacy, stigma, and medication adherence. Patients and methods This cross-sectional study adopted a convenient sampling method to survey 221 patients with multimorbidity who attended the general practice department of a tertiary hospital in Beijing, China, from March to October 2023. A self-designed questionnaire was used to collect the patients' sociodemographic data; the Chinese version of the Medication Literacy Scale (C-MLS), Stigma Scale for Chronic Illness (SSCI), and Morisky Medication Adherence Scale were applied to assess their medication literacy, stigma, and medication adherence, respectively. As medication adherence score, medication literacy, and stigma were all continuous variables, analysis of variance (ANOVA) was employed for univariate analysis. To examine the associations among these three variables, pairwise correlation analysis was first performed, followed by mediation analysis to explore their intrinsic relationships. Model fit was evaluated using the Root Mean Square Error of Approximation (RMSEA), Comparative Fit Index (CFI), Normed Fit Index (NFI), and Tucker-Lewis Index (TLI); RMSEA < 0.08 and CFI, NFI, TLI all > 0.90 indicated a good model fit. Results A total of 221 patients with multimorbidity were included: 123 (55.66%) with 2–3 concurrent chronic diseases, 72 (32.58%) with 4–5, and 26 (11.76%) with ≥6 chronic conditions. Stigma was negatively associated with medication adherence ( r = −0.259, p < 0.001) and medication literacy ( r = −0.293, p < 0.001), while medication adherence was positively associated with medication literacy ( r = 0.188, p < 0.01). Mediation analysis indicated a well-fitted model (χ 2 /df = 1.12, CFI = 0.997, TLI = 0.992, RMSEA = 0.024, SRMR = 0.041). The indirect association between stigma and medication adherence via medication literacy was significant [β = −0.045, SE = 0.022, 95% CI = (−0.095, −0.001)]. Conclusions Medication literacy, stigma, and medication adherence were closely correlated, and medication literacy may serve as an intermediate variable in the relationship between stigma and medication adherence.