Depression does not moderate the association between beliefs about medicines and medication adherence in patients with rheumatoid arthritis: A longitudinal study.

Non-adherence is common in people with rheumatoid arthritis (RA). According to the 'necessity-concerns framework', beliefs about the necessity and concerns about prescribed medications influence adherence. The present study's objective was to investigate whether depression moderates associations between beliefs about medicines and adherence among people with physician-diagnosed RA in a longitudinal study (N = 361; 31% male, mean age [SD] 60.2 [13.4]). Adherence (adherent vs non-adherent; MARS), beliefs about medicines (BMQ), and depression (HADS) were assessed at baseline, 3- and 12-month follow-up. Multivariate logistic regression models were calculated (predictors: necessity/concerns, depression; outcome: adherence). Two-thirds of patients were non-adherent. No significant interactions were found between necessity/concerns and depression. Contrary to previous cross-sectional research, we did not find evidence for a moderating role of depression in associations between beliefs about medicines and adherence. Possible moderating effects of depression might be less robust than previously thought and therefore harder to detect in longitudinal analyses.