Sex differences in self‐harm and suicide in young autistic adults.

Introduction: Both suicide and self‐harm are disproportionately common in autistic people. Sex differences in risk of self‐harm and suicide are observed in the general population, but findings are mixed for autistic people. Self‐cutting may be a particularly risky self‐harm behaviour for suicide in autistic people. We aimed to explore sex differences and differences in method of self‐harm in the association between self‐harm and suicide in autistic and non‐autistic adolescents and young adults. Methods: We used a total population register of 2.8 million Swedish residents. Participants were followed from age 12 until December 2021 for medical treatment because of self‐harm, and death from suicide. We used Cox proportional hazard regression models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of death from suicide following self‐harm, and Relative Excessive Risk due to Interaction (RERI) to explore the interaction between self‐harm and autism in females and males. Results: We identified 85,143 autistic individuals (31,288 female; 53,855 male) and 2,628,382 non‐autistic individuals (1,286,481 female; 1,341,901 male) aged 12–37 years. Incidence of suicide following self‐harm was higher in autistic males (incidence per 100,000 risk‐years = 169.0 [95% CI 135.1, 211.3]) than females (125.4 [99.4, 158.3]). The relative risk was higher for autistic females (HR 26.1 [95% CI 20.2, 33.7]) than autistic males (12.5 [9.9, 15.8]). An additive effect of both autism and self‐harm was observed in both females (RERI = 9.8) and males (2.0). Autistic individuals who self‐harmed through cutting were at greatest risk of death from suicide (HR 25.1 [17.9, 35.2]), compared to other methods. Conclusion: Autistic males and females are at increased risk of death from suicide following severe self‐harm, particularly self‐cutting. [ABSTRACT FROM AUTHOR]