Mental Health Service Use in Sexually and Gender Diverse Youths and Cisgender Heterosexual Youths.

Importance: Sexually and gender diverse (SGD) youths experience disproportionate mental health challenges, yet longitudinal evidence of their mental health service use remains limited. Objective: To examine mental health outpatient, emergency, and inpatient service use among SGD youths compared with cisgender heterosexual youths from preschool to young adulthood. Design, Setting, and Participants: This population-based cohort study included 1326 participants from the Quebec Longitudinal Study of Child Development who self-reported sexual orientation and gender identity at age 23 years. Participants were followed up from birth (between October 1997 and July 1998). The wave of data collection when they were 23 years old occurred in June 2023. Data analyses were conducted between September 2024 and June 2026. Exposure: Self-reported sexual and gender diversity at age 23 years. Main Outcomes and Measures: Mental health outpatient (age 1-23 years; 1997-1998 to 2021), emergency (age 18-23 years; 2016 to 2021), and inpatient (age 8-23 years; 2006 to 2021) service use extracted from 3 provincial administrative health databases: the Régie de l'Assurance Maladie du Québec, the Banque de Données Communes des Urgences, and the Maintenance et Exploitation des Données pour l'Étude de la Clientèle Hospitalière. Results: Of 1326 participants (691 [52.1%] assigned female at birth), 324 (24.4%) identified as sexually diverse and 32 (2.4%) identified as gender diverse. After controlling for sex assigned at birth and socioeconomic status, SGD youths were more likely than cisgender heterosexual youths to use outpatient services (adjusted odds ratio [AOR], 1.41 [95% CI, 1.09-1.83]) and emergency services (AOR, 1.99 [95% CI, 1.33-2.98]); the association was not present for inpatient services (AOR, 1.49 [95% CI, 0.87-2.54]). Growth curve models indicated a similar likelihood of outpatient service use between SGD youths and cisgender heterosexual youths in preschool, but steeper increases among SGD youths over time (b = 0.21 [SE, 0.11; 95% CI, -0.002 to 0.41]; P = .05]). SGD youths assigned female at birth had higher odds of emergency and inpatient service use compared with cisgender heterosexual females. SGD youths assigned male at birth had higher odds of outpatient service use compared with cisgender heterosexual males. Conclusions and Relevance: In this population-based cohort study, SGD youths showed greater use of mental health services across development, with disparities emerging early and widening over time. These findings highlight the need for early and sustained mental health support for SGD youths.