Self-Harm Events and Suicide Deaths Among Autistic Individuals in Ontario, Canada

Abstract

ImportanceReasons for elevated suicide risks among autistic people are unclear, with insufficient population-based research on sex-specific patterns to inform tailored prevention and intervention.ObjectivesTo examine sex-stratified rates of self-harm events and suicide death among autistic individuals compared with nonautistic individuals, as well as the associated sociodemographic and clinical risk factors.Design, Setting, and ParticipantsThis population-based matched-cohort study using linked health administrative databases in Ontario, Canada included all individuals with physician-recorded autism diagnoses from April 1, 1988, to March 31, 2018, each matched on age and sex to 4 nonautistic individuals from the general population. Self-harm events resulting in emergency health care from April 1, 2005, to December 31, 2020, were examined for one cohort, and death by suicide and other causes from April 1, 1993, to December 31, 2018, were examined for another cohort. Statistical analyses were conducted between October 2021 and June 2023.ExposurePhysician-recorded autism diagnoses from 1988 to 2018 from health administrative databases.Main Outcomes and MeasuresAutistic and nonautistic individuals who were sex stratified a priori were compared using Andersen-Gill recurrent event models on self-harm events, and cause-specific competing risk models on death by suicide or other causes. Neighborhood-level income and rurality indices, and individual-level broad diagnostic categories of intellectual disabilities, mood and anxiety disorders, schizophrenia spectrum disorders, substance use disorders, and personality disorders were covariates.ResultsFor self-harm events (cohort, 379 630 individuals; median age at maximum follow-up, 20 years [IQR, 15-28 years]; median age of first autism diagnosis claim for autistic individuals, 9 years [IQR, 4-15 years]; 19 800 autistic females, 56 126 autistic males 79 200 nonautistic females, and 224 504 nonautistic males), among both sexes, autism diagnoses had independent associations with self-harm events (females: relative rate, 1.83; 95% CI, 1.61-2.08; males: relative rate, 1.47; 95% CI, 1.28-1.69) after accounting for income, rurality, intellectual disabilities, and psychiatric diagnoses. For suicide death (cohort, 334 690 individuals; median age at maximum follow-up, 19 years [IQR, 14-27 years]; median age of first autism diagnosis claim for autistic individuals, 10 years [IQR, 5-16 years]; 17 982 autistic females, 48 956 autistic males, 71 928 nonautistic females, 195 824 nonautistic males), there was a significantly higher crude hazard ratio among autistic females (1.98; 95% CI, 1.11-3.56) and a nonsignificantly higher crude hazard ratio among autistic males (1.34; 95% CI, 0.99-1.82); the increased risks were associated with psychiatric diagnoses.Conclusions and RelevanceThis cohort study suggests that autistic individuals experienced increased risks of self-harm events and suicide death. Psychiatric diagnoses were significantly associated with the increased risks among both sexes, especially for suicide death, and in partially sex-unique ways. Autism-tailored and autism-informed clinical and social support to reduce suicide risks should consider multifactorial mechanisms, with a particular focus on the prevention and timely treatment of psychiatric illnesses.

Are autistic females at greater risk of suicide? A call for clarity to advance suicide prevention for the whole community

“…However, two large and more recent studies identified differences in suicide attempt risk with autistic females at greater risk than autistic males (Hirvikoski et al, 2020;Kõlves et al, 2021). Martini et al (2022) and Lai et al (2023) also both found higher risk for autistic females than males when examining self-harm codes. Hand et al (2020) found no differences between autistic males and females when looking at suicidal ideation.…”

“…Suicide risk is a general phrase that is often used to refer to the risk of a wide range of suicidal behaviors. Existing evidence about autistic suicide risk includes studies using a variety of metrics including death by suicide (e.g., Hirvikoski et al, 2016;Kirby et al, 2019;Lai et al, 2023), suicide attempts (i.e., actions taken with the intent of dying; e.g., Hirvikoski et al, 2020;Kõlves et al, 2021), and suicidal thoughts or feelings (e.g., Cassidy et al, 2014). Not all suicide metrics have the same prevalence or associations, so it is imperative that the studied outcome is defined.…”

“…The study summaries presented in Table 1 demonstrate that there is a fair amount of consistency across population-derived studies looking at sex differences in autistic suicide risk. The five studies that have looked at differences in risk of suicide death (Hirvikoski et al, 2016(Hirvikoski et al, , 2020Kirby et al, 2019;Lai et al, 2023;Tsai et al, 2023) have consistently shown that autistic people (analyzed with sex groups combined) are at greater risk than their non-autistic counterparts. However, these studies also consistently show that within the autistic population, autistic males and females have similar risk of dying by suicide (i.e., no significant differences between autistic male and female risk, demonstrated by overlapping confidence intervals).…”