Abstract
Background Comorbid substance use disorder (BD-SUD) is common among individuals with bipolar disorder (BD) and is associated with worse clinical outcomes. This study compares differences in medication adherence, adherence barriers, and symptom severity of individuals with BD-SUD based on diagnostic status (current, past, or none).Methods This interim analysis utilized screening and baseline data from a 12-month randomized controlled trial comparing adherence interventions among poorly adherent individuals with BD. Patients were recruited from public mental health settings and met strict diagnostic and symptom criteria.Results From the study sample (N = 129; Mage = 42.18; SDage = 13.04), no significant sociodemographic differences were found. Individuals with BD and current substance use disorder reported significantly higher rates of problematic substance use and motivation to reduce such use compared to the other groups. No other differences were found.Conclusions Comorbid substance use disorder is common among individuals with bipolar disorder and often associated with poor outcomes. In this baseline, cross-sectional analysis, minimal differences were observed across varying BD-SUD status. Longitudinal analyses will be important for clarifying whether adherence and related outcomes differ over time across BD-SUD groups.