Sex differences in post-traumatic stress disorder risk among autistic individuals: a population-based matched cohort...

Autistic individuals may experience elevated risk for post-traumatic stress disorder (PTSD). Although autism is more commonly diagnosed in males, females in the general population develop PTSD at approximately twice the rate, raising the question of whether autistic females face a particularly elevated burden. We examined the association between autism and incident PTSD, characterized sex differences in risk, identified high-risk subgroups, and described post-diagnosis clinical trajectories.

We conducted a population-based matched cohort study using Swedish national registers. All individuals born in Sweden from 1990 through 2010 were identified through the Medical Birth Register and followed from birth through December 31, 2017, death, or emigration. Autistic individuals (N = 49,049) were matched up to 1:10 to non-autistic individuals (N = 461,972) on sex and birth year. Cox proportional hazards regression with age as the underlying time scale estimated hazard ratios (HRs) for incident PTSD (ICD-9 code 309.81; ICD-10 F43.1), with models stratified by matched set and robust standard errors clustered on biological mother. Among individuals who developed PTSD, we compared care utilization, hospitalization rates, and persistence of care contacts.

During a mean follow-up of 5.5 years, 411 autistic individuals (0.8%) and 942 non-autistic individuals (0.2%) developed PTSD. Autism was associated with a 4.3-fold increased risk of incident PTSD (HR = 4.27; 95% CI, 3.85-4.74). Risk was higher among females (HR = 4.61; 95% CI, 4.09-5.20) than males (HR = 3.47; 95% CI, 2.81-4.27; P for interaction = .02). Among autistic individuals, co-occurring ADHD conferred additional risk (HR = 1.43; 95% CI, 1.17-1.73). Joint sex-ADHD stratification revealed marked heterogeneity: relative to autistic males without ADHD, HRs were 1.84 for males with ADHD, 7.42 for females without ADHD, and 10.46 for females with ADHD, with 10-year cumulative incidence reaching 5.7% among autistic females with ADHD. Autistic individuals with PTSD had higher care utilization (mean visits: 5.6 vs 4.6; P < .001), more psychiatric hospitalizations (27.5% vs 20.5%; P = .006), and more persistent care contacts (24.8% vs 13.9%; P = .006).

Autism is associated with substantially elevated PTSD risk, particularly among females with co-occurring ADHD. When PTSD occurs, autistic individuals experience more severe and persistent clinical courses, supporting targeted screening and sustained follow-up.