Autism symptoms in Attention-Deficit/Hyperactivity Disorder: a familial trait which correlates with conduct, oppositional defiant, language and motor disorders.

Mulligan et al. (2009) looked at families already diagnosed with ADHD. They asked: do autism traits run in these families too?

They used math models to sort the families into hidden groups. Then they counted who had extra autism signs, conduct problems, speech delays, and motor issues.

One small group—about 7 out of every 100 ADHD families—showed high autism traits. These same families also carried more conduct, language, and motor disorders.

The pattern looked inherited: autism signs clustered among brothers, sisters, and parents in the same household.

Green et al. (2015) repeated the idea in a regular school sample and still found more autism traits in kids with ADHD. Their result supports the link outside of special clinics.

Reus et al. (2013) flipped the lens: when kids already have ASD, adding ADHD makes parent and interview ratings shoot up. It warns us that ADHD hype can inflate autism scores, so we need direct tests too.

Berenguer et al. (2018) and Tonizzi et al. (2022) show the same mixed group suffers a double hit—worse executive function, theory-of-mind, and daily living skills—explaining why Aisling’s 7% look so complicated in therapy.

If you serve a child with ADHD, screen for autism red flags. Roughly one in every fourteen will land in the severe overlap zone and will need broader plans—speech, motor, behavior, and self-help goals—than straight ADHD protocols.