Persistent Patterns of Licit and Illicit Drug Use Among Gender and Sexuality Diverse Women in Australia: Results From a Prospective Cohort Study

INTRODUCTION: Gender and sexuality diverse women consistently report higher rates of licit and illicit drug use than heterosexual women. Longitudinal data are essential to understanding these patterns yet remain limited. We established a cohort to examine prevalence and changes in use. METHODS: We conducted a prospective cohort study, the Understanding Lesbian, Bisexual and Queer Women's Alcohol, Drug Use and Health (UnLEASH) study, with data collected at baseline (May-October 2021) and follow-up (August-November 2022). Participants self-reported past-4-week, past 12 months and lifetime use of alcohol, tobacco, e-cigarettes and illicit drugs, including non-medical use of prescription medications. Prevalence was calculated at each wave. McNemar's tests assessed within-subject change with Bonferroni correction. RESULTS: Among 1080 participants, 89.4% were cisgender women, 4.7% transgender women and 5.8% non-binary; 51.4% identified as lesbian, 21.9% bisexual, 16.3% queer and 10.3% used another term. Baseline past-4-week use was: tobacco 20.4%, e-cigarettes 11.2% (76% containing nicotine), alcohol 77.1% and any illicit drug 23.6% (most of which was non-medical cannabis use at 18.8%). Among 458 follow-up participants, tobacco use declined (18.3% to 12.7%, p < 0.001). Among 178 who had ceased tobacco smoking at or before baseline, 7.3% had initiated e-cigarette use, 10.7% continued use and 19.7% had ceased use. No significant changes were observed for other drugs. DISCUSSION AND CONCLUSIONS: Substance use remained persistently high and stable, even as population-level trends decline. These findings raise questions about how high prevalence is interpreted, suggesting it may not necessarily indicate problematic use, but instead reflect long-term, embedded patterns shaped by community and social contexts.