Co-Occurrence of ADHD and Autism: Prevalence, Presentation, and Clinical Implications

How often do ADHD and autism actually occur together? Often enough that treating them as separate, rarely-overlapping conditions turns out to be one of the bigger blind spots in how adults get assessed.

What the research shows

Estimates vary with the sample and the method used, but reviews consistently land on the same conclusion: a large share of autistic people also meet criteria for ADHD, and a substantial minority of people with ADHD are autistic. The exact percentages differ between studies — clinical samples, community samples, and child-versus-adult cohorts all produce different numbers — but the direction is unambiguous. This is a high-overlap pair, not a rare coincidence. The peer-reviewed review linked from this page (see "Visit source") walks through the figures and how they were derived.

The takeaway for an individual isn't a number. It's that if you've been diagnosed with one of these conditions, the base rate of also having the other is high enough to be worth taking seriously rather than dismissing.

Why it was under-counted for so long

Two forces kept the co-occurrence rate looking smaller than it is. First, the diagnostic rules: until the DSM-5 in 2013, clinicians were not permitted to diagnose ADHD and autism in the same person, so the overlap literally could not be recorded. Decades of records simply don't contain it.

Second, the traits hide each other. Mutual masking means a co-occurring profile often presents as a milder, blurrier version of either condition alone — enough to look sub-threshold on a single-axis tool and never get the second diagnosis. Groups who were already under-identified, like autistic and AuDHD women, were hit hardest by both forces at once.

Where to go from here

For the everyday version of this topic, see the ADHD–autism overlap. To understand how we score the overlap directly rather than inferring it from two separate tests, read our methodology — the AuDHD axis exists precisely because co-occurrence is this common.

What percentage of autistic people have ADHD?

Published estimates range widely depending on the population studied, but reviews consistently report that a large proportion of autistic individuals also meet ADHD criteria — far above the rate in the general population. Because the figures depend heavily on methodology, we point to the peer-reviewed source rather than quoting a single number.