Short report: Patterns of motor difficulties among autistic, ADHD, or Autistic-ADHD youth in Iceland

Res Dev Disabil. 2026 Jul 4;175:105338. doi: 10.1016/j.ridd.2026.105338. Online ahead of print.

ABSTRACT

BACKGROUND: Research indicates motor delays in youth with ADHD or autism, but patterns in co-occurring ADHD and autism remain under-explored. This study compared motor performance in youth with co-occurring conditions with that of single-diagnosis groups.

METHODS: A sample of 122 stimulant medication naïve children in Iceland (Mage = 9.06 ± 1.95 years) diagnosed with ADHD (n = 77), autism (n = 15), or both (n = 30), without intellectual impairment, was assessed using the Movement Assessment Battery for Children-Second Edition.

RESULTS: Kruskal-Wallis test results showed a significant effect for percentile rank, with post-hoc comparisons revealing the Autism group scored significantly lower than both the ADHD and Autism + ADHD groups. Similarly, for the total test score, significant differences were found, with the Autism group again scoring lower than both the ADHD and Autism + ADHD groups. Across subscales, significant group effects were found for Balance, where the Autism group underperformed both the ADHD and Autism + ADHD groups; Aiming and Catching, where the Autism group scored lower than the ADHD group; and Manual Dexterity, where the Autism group scored lower than the Autism + ADHD group. No significant differences were found between the ADHD and Autism + ADHD groups on any measure.

CONCLUSION: Youth with co-occurring ADHD and autism demonstrate motor performance levels similar to those with ADHD only, with both groups outperforming the Autism group. These findings suggest that the presence of ADHD symptoms may relate to distinct motor trajectories in autism.

PMID:42401139 | DOI:10.1016/j.ridd.2026.105338