Sex differences in depression diagnosis, primary care contacts, and overdose risk

Background: British Columbia (BC) first declared drug poisoning (overdose) a public health emergency in 2016. Ten years later, the province continues to report the highest rates of both fatal and non-fatal overdose in Canada, with sex disparities in overdose trends. Depression and substance use disorder (SUD) are known overdose risk factors, however population-level evidence on potential sex-specific associations between depression history and overdose risk, and in the role of post-overdose mental health care in reducing overdose recurrence, remains limited. Methods: Linked administrative health data from the Provincial Health Services Authority’s Platform for Analytics and Data were analysed. This analysis used a retrospective cohort design to estimate sex-specific incidence rate ratios for fatal and non-fatal overdose (2015-2024) among adults classified by documented depression and/or SUD diagnosis history (2010-2014). This analysis also used a nested-case control design with incidence density sampling among people with a history of a depression diagnosis who experienced a non-fatal overdose, to estimate sex-stratified incidence rate ratios for the association between the presence and the number of primary care contacts for mental health within 30 or 90 days of first overdose, and risk of recurrent overdose. Results: Documented depression, SUD, and co-occurring depression and SUD diagnosis histories were associated with elevated overdose risk relative to those with neither diagnosis. Relative associations were stronger among females than males, despite absolute incidence of both fatal and non-fatal overdose being lower among females. Primary care contacts for mental health within 30 days of an overdose were significantly associated with reductions in recurrent overdose risk for both sexes; associations were weaker at 90 days. Conclusions: The associations between documented depression history and overdose risk differed by sex. Timely access to primary care for mental health was associated with a reduction in recurrent overdose risk among both males and females with a history of a depression diagnosis. These findings highlight the importance of sex and gender-based analysis for improving the precision of overdose risk estimation and intervention design for both males and females, and point to role of timely mental health care for both overdose prevention efforts and post-overdose care pathways.