Epidemiology of autism in adults across age groups and ability levels

Background: The epidemiology of autism in adults has relied on untested projections using childhood research. Aims: To derive representative estimates of the prevalence of autism and key associations in adults of all ages and ability levels. Method: Comparable clinical diagnostic assessments of 7274 Adult Psychiatric Morbidity Survey participants combined with a population case-register survey of 290 adults with intellectual disability. Results: The combined prevalence of autism in adults of all ages in England was 11/1000 (95% CI 3–19/1000). It was higher in those with moderate to profound intellectual disability (odds ratio (OR) = 63.5, 95% CI 27.4–147.2). Male gender was a strong predictor of autism only in those with no or mild intellectual disability (adjusted OR = 8.5, 95% CI 2.0–34.9; interaction with gender, P = 0.03). Conclusions: Few adults with autism have intellectual disability; however, autism is more prevalent in this population. Autism measures may miss more women with autism.