How Often Do Autism and ADHD Co-Occur?

Some genes are associated with both attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). To learn more about the frequency of comorbidity and familial aggregation, researchers analyzed population-level data in Sweden involving 1.9 million people born between 1987 and 2006.

Only the combined type of ADHD was analyzed. There were 28,468 individuals (1.5%) with ASD diagnosed at age ≥1 year and 82,398 (4.3%) diagnosed at age ≥3 years with ADHD. Both disorders occurred more frequently in males. Overall, 48% of people with ASD had ADHD, and 17% of those with ADHD had ASD. Risk for ADHD was 22 times greater among those with ASD than among those without ASD. Having ASD but not intellectual disability significantly incr…