Mental health disorders and suicide risk among autistic children, adolescents and adults: a population-based study using linked administrative data

Background: Autistic people face elevated mental health risks, yet few population-based studies have quantified these risks across developmental stages. We examined the prevalence and relative risk of physician-diagnosed mental health disorders and suicide attempts among autistic individuals in the province of Manitoba, Canada, using linked administrative health data. Methods: We conducted a whole-population cohort study using provincial health records from 2018 to 2022. Autistic individuals were identified using a validated case definition and compared to all other Manitobans without autism. We assessed five-year prevalence and sex- and age-adjusted relative risks of attention-deficit hyperactivity disorder (ADHD), conduct disorder, mood/anxiety disorders, schizophrenia, substance use disorders, and suicide attempts across three age groups (6-12, 13-17, and 18-45 years) using regression models. Findings: Autistic people had substantially higher prevalence of all examined mental health disorders (except substance use disorder) and significantly elevated relative risks across every age group we examined. Compared to non-autistic individuals, autistic people had higher risks of ADHD (age- and sex-adjusted relative risk [aRR] 5.24, 95% confidence interval [CI] 4.82-5.70), conduct disorder (aRR 5.96, 95% CI 4.61-7.70), mood/anxiety disorders (aRR 2.00, 95% CI 1.89-2.12), schizophrenia (aRR 9.82, 95% CI 8.94-10.78), and attempted suicide (aRR 3.14, 95% CI 2.31-4.27). The study cohort included n = 317,073 males and n = 314,261 females. Autistic males (n = 4523) had higher risk of being diagnosed with ADHD (aRR 1.39, 95% CI 1.35-1.43), conduct disorder (aRR 1.54, 95% CI 1.34-1.78), and schizophrenia (aRR 1.83, 95% CI 1.71-1.96), whereas autistic females (n = 1377) had higher risk of mood/anxiety disorders (aRR 1.96, 95% CI 1.87-2.00) and attempted suicide (aRR 2.22, 95% CI 2.00-2.44). Interpretation: Autistic individuals experience disproportionate mental health challenges, including suicide risk, across their life course. These findings demonstrate the urgent need for sex-specific, autism-informed mental health strategies, early routine screening, and specialized clinical training to improve diagnostic assessment and care delivery in universal health systems. Funding: We gratefully acknowledge the support of the Azrieli Foundation, the National Centre for Autism Collaboration, the Autism Alliance of Canada, and the Canadian Institutes of Health Research.