Association between opioid agonist therapy and pharmacotherapy for mental disorders among people living with HIV and co-occurring opioid use and mental disorders.

BACKGROUND: People living with HIV (PLWH) with co-occurring opioid use disorder (OUD) and mental disorders experience fragmented care. Opioid agonist therapy (OAT) is central to treating OUD and improves engagement in HIV care; however, its role in facilitating mental disorder pharmacotherapy is unclear. This study examined (1) the relationship between overall OAT exposure and psychotropic dispensations, and (2) whether measures of OAT engagement (adherence and induction completion) were associated with psychotropic dispensations. METHODS: We conducted a retrospective population-based cohort study using data from the Comparative Outcomes and Service Utilization Trends cohort in British Columbia, Canada (2012-2020). For Aim 1, psychotropic dispensing was modelled as a rate per person-year across the cohort. For Aim 2, analyses were restricted to OAT recipients, modelling count of psychotropic dispensations per OAT episode in relation to adherence and induction completion. Mixed-effects negative binomial regression models were applied for both aims. RESULTS: Among 17,119 PLWH, 1,486 (8.7%) had co-occurring OUD and a mental disorder, of whom 1,177 (79.2%) received OAT. OAT exposure was significantly associated with psychotropic dispensing rates (Rate Ratio 3.11; 95% CI: 2.74, 3.53). Higher OAT adherence showed a dose-response relationship, with a sixfold increase in psychotropic dispensing at ≥90%. Induction completion was associated with increased psychotropic dispensing per episode (Count Ratio 2.24; 95% CI: 1.94, 2.57). CONCLUSION: Overall OAT exposure and greater measures of OAT engagement were strongly associated with psychotropic pharmacotherapy. These findings suggest that sustained OAT engagement may provide a longitudinal platform for integrating mental health care within OAT services.