Clinical and Sociodemographic Correlates of Poor Medication Adherence in People With Bipolar Disorder: A Systematic Review and Meta-Analysis

Objectives: Poor adherence to psychopharmacological treatment may contribute to relapses in bipolar disorder (BD). We performed a systematic review and meta-analysis to identify factors associated with poor adherence in BD. Methods: The protocol was registered in Open Science Framework Registries (https://doi.org/10.17605/OSF.IO/2KZFJ). We searched main electronic databases through March 2025. Random-effects meta-analyses were performed to obtain pooled odds ratios (ORs) and standardized mean differences (SMDs) for relevant correlates. Results: We included 19 studies. Subjects with poor adherence were more likely to be younger (SMD = −0.22, 95% CI: −0.42–−0.02) and to have lower education (SMD = −0.34, 95% CI: −0.55–−0.12), and less likely to be in a relationship (OR = 0.54, 95% CI: 0.34–0.86). Moreover, earlier age at onset (SMD = −0.29, 95% CI: −0.53–−0.04), psychotic features (OR = 1.58, 95% CI: 1.30–1.92), a history of suicide attempts (OR = 1.36, 95% CI: 1.03–1.78), a higher number of manic (SMD = 0.34, 95% CI: 0.08–0.61) and mixed (SMD = 0.16, 95% CI: 0.03–0.28) episodes, and more hospitalizations (SMD = 0.53, 95% CI: 0.32–0.73) all emerged as correlates of poor adherence. Also, cannabis (OR = 2.34, 95% CI: 1.79–3.07) and alcohol use disorders (OR = 1.71, 95% CI: 1.39–2.12), comorbid generalized anxiety disorder (OR = 3.70, 95% CI: 1.90–7.22), and comorbid personality disorders (OR = 5.54, 95% CI: 1.32–23.15) were associated with poor adherence. Finally, poorly adherent individuals had higher global severity (SMD = 0.21, 95% CI: 0.01–0.41), lower insight (SMD = −0.74, 95% CI: −1.08–−0.41), and lower global functioning (SMD = −0.60, 95% CI: −0.87–−0.34). No differences were estimated for other variables. Conclusions: This meta-analysis showed that poor adherence in people with BD is associated with specific correlates. Although evidence was generally weak due to small effect sizes, imprecision, inconsistency, and potential publication bias, our findings highlight the importance of strategies to improve adherence.