Brief report: prevalence of attention deficit/hyperactivity disorder among individuals with an autism spectrum disorder.

Hanson et al. (2013) asked parents and teachers about ADHD signs in 1,838 kids already diagnosed with autism.

They counted how many children met the cutoff for "clinically significant" ADHD symptoms on rating scales.

Parent forms alone flagged 16% of the group. When both parent and teacher had to agree, the rate dropped to 2%.

The big lesson: one rater can over-estimate how many kids truly have both ASD and ADHD.

Canals et al. (2024) later ran a whole-school survey and found only 0.5% of children met DSM-5 criteria for both disorders. Their stricter, dual-diagnosis method supports Ellen’s low 2% figure and updates it with newer rules.

Green et al. (2015) flipped the question. They started with kids who had ADHD and then looked for ASD traits. They still found plenty of overlap, showing the link runs both ways.

Wilmut et al. (2013) did the same thing in adults and saw high ADHD symptoms in over a third of ASD cases. Together these papers stretch the comorbidity picture across age groups.

If you screen a child with ASD for ADHD, collect at least two informants before you label it "combined." A single rating can double the apparent rate and may lead to unneeded medication or goals. When numbers look high, pause and gather teacher data; the second source often brings the picture in line with true DSM-5 base rates.