The short-term effectiveness of antidepressants in a transdiagnostic sample and determinants of side effects and medication nonadherence: an observational study

Antidepressants are widely prescribed, yet evidence on their short-term effectiveness and tolerability in routine outpatient psychiatric care remains limited. This observational study followed 123 patients newly initiated or switched to an antidepressant in a university hospital outpatient clinic to examine early-term side effects, their associations with treatment discontinuation, and predictors of short-term response in a pragmatic routine-care setting. Depression and anxiety symptoms, sociodemographic variables, and functionality were assessed at baseline; side effects and adherence were evaluated through structured interviews during the first month; and treatment response was determined at follow-up. The remission rate at one month was 72.3%, while 12.3% showed no response. Higher pretreatment anxiety levels predicted greater severity of early side effects, and lower baseline functionality predicted poorer adherence. Patients who achieved response or remission were more likely to report at least one side effect. These findings suggest that many patients struggle to maintain antidepressant treatment during the early phase, and that anxiety and functional impairment influence both tolerability and adherence. Early psychoeducation, close monitoring, and tailored support for patients with elevated anxiety or reduced functionality may improve continuity of treatment and reduce the risk of delayed recovery.