The Deficits Look the Same on Paper

What the research found

Executive function is the family of mental skills that let a child hold a goal in mind and get there: paying attention, resisting the first impulse, switching between tasks, keeping instructions in working memory, planning ahead. Weaknesses in these skills are common in both autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). A long-standing question is whether the two conditions produce *different* executive-function profiles, or much the same one. If they differed, a cognitive test might help tell them apart.

Parker Townes and colleagues set out to answer this by pooling the studies that had already put the question to a direct test. Rather than compare autistic children in one study with children who have ADHD in another, they looked only at studies that measured both groups, on the same tasks, at the same time. That design matters. It removes many of the differences in equipment, scoring and setting that make cross-study comparisons unreliable.

They identified 58 studies, covering 8,259 individuals: 2,092 with autism, 2,800 with ADHD, and 3,367 typically developing peers as a comparison group. This is a large body of evidence for a question of this kind, and it was assembled through a systematic review and meta-analysis, meaning the results were combined statistically rather than simply summarised.

The central finding is a negative one, and it is worth stating plainly. Across every executive-function domain they examined, the researchers found no reliable difference between the autism and ADHD groups. On attention, on cognitive flexibility, on visuospatial ability, on working memory, on processing speed, on response inhibition, the two conditions performed alike. Whatever distinguishes autism from ADHD, these tests did not capture it.

The two groups did differ from their typically developing peers. Both autistic children and children with ADHD performed worse than the comparison group on almost all of the domains listed above. The one exception was planning. On planning tasks, the clinical groups did not differ from typically developing children. So the picture is a shared pattern of difficulty relative to peers, with planning standing apart, and no gap between the two diagnoses themselves.

The authors are careful about what this rests on. Many of the individual analyses drew on a small number of studies and participants, which meant they could not properly test whether factors like age changed the results. They report large variation between studies and low external validity, which is a way of saying the findings may not transfer cleanly to every child in every setting. Few studies accounted for children who have both conditions, or who sit somewhere on the spectrum of traits without a formal diagnosis.

What it means for you and your child

The most useful thing this study offers a parent is a note of caution about one particular hope. It is tempting to imagine that a cognitive test could settle whether a child “really” has autism or ADHD. On the evidence here, executive-function testing cannot do that. The two conditions leave much the same footprint on these tasks. A test that shows weak working memory or poor impulse control tells you something real, but it does not tell you which diagnosis is behind it.

That does not make diagnosis guesswork. It means diagnosis rests where it always has: on a careful account of how your child behaves across settings, over time, in the words of the people who know them. Autism and ADHD are distinguished by patterns of social communication, interests, activity and attention in daily life, not by a score on a flexibility task. If a clinician spends time gathering that fuller picture rather than leaning on a single test, that is the process working as it should.

For the day-to-day, there is a quiet reassurance in the shared pattern. If your child struggles to hold instructions in mind, to shift between activities, or to wait before acting, those difficulties are well documented and widely shared, whichever label applies. The supports that help are largely the same: breaking tasks into steps, reducing what has to be held in memory at once, giving clear warning before transitions, and building in structure rather than relying on willpower. You do not need to know the precise diagnosis to start using them.

The finding on planning deserves a measured reading. That the clinical groups matched their peers on planning tasks does not mean planning is a strength, or that your child will plan well in real life. Laboratory planning tasks are narrow and tidy in a way that homework, mornings and long-term projects are not. The result tells us these particular tests did not detect a deficit; it does not promise smooth organisation at home.

It is worth holding the limits of the study in view. A meta-analysis summarises what has been measured; it cannot reveal what the studies did not look at. Most of the children studied had a single, clear diagnosis, yet many real children carry traits of both conditions at once. The authors themselves flag how little of this overlap the evidence covers. And a meta-analysis, however large, describes groups on average. Your child is one person, and the average conceals a great deal of variation.

None of this speaks to cause. The study shows that autism and ADHD look similar on these measures; it does not explain why, nor whether the same underlying processes are involved. Similar performance can arise from different roots. The honest summary is narrow and steady. On direct comparison, these two conditions share an executive-function profile that sits below that of typically developing peers, planning aside. That is what the evidence supports, and it is enough to guide how we test, how we diagnose, and how we help, without asking a cognitive score to carry more than it can.