Sibling Outcomes Among Probands with Autism Spectrum Disorder: A Population-wide Longitudinal Cohort Study

Living with an Autistic sibling presents unique challenges for their siblings. Previous literature reports increased psychiatric problems in siblings of autistic probands, but other areas of functioning remain underexplored at the population-level. This study investigates whether these siblings have different rates of mental disorders, hospitalized suicide attempts, psychotropic medication prescriptions, physical health burden, and educational outcomes against siblings of Down Syndrome probands and siblings of individuals without neurodevelopmental disorders (Neurotypical). Using population-based administrative data, three longitudinal matched cohorts evaluated outcomes over a 10-24-year follow-up. After accounting for covariates, siblings of autistic probands (N = 5,409) evidenced increased risk of all mental disorders except substance use disorder versus siblings of Neurotypical probands (N = 328,015), and increased risk of select disorders versus siblings of Down Syndrome probands (N = 3,952). Siblings of autistic probands were more likely to be prescribed psychotropic medications than either comparator and more likely to experience developmental delays than siblings of Neurotypical probands.