Comorbid ADHD and DCD: examining cognitive functions using the WISC-IV.

Loh et al. (2011) compared WISC-IV scores across four groups of late-elementary kids: ADHD only, DCD only, ADHD plus DCD, and typical peers.

They used a quasi-experimental design. No random assignment—just careful group matching.

Kids with DCD, with or without ADHD, scored lower on the Perceptual Reasoning Index. Kids with ADHD alone did not.

The pattern points to a visuo-spatial weakness tied to DCD, not to ADHD.

Kanevski et al. (2023) extends the same comorbid group and finds weaker visuospatial working memory yet normal math scores. They show kids compensate through different cognitive routes.

Dionne et al. (2024) also extend the DCD story: visuoperceptual skills drive math underachievement, adding academic risk to the visuospatial profile.

Wuang et al. (2011) complement the finding by showing DCD kids struggle on the Wisconsin Card Sorting Test—so executive function, not just perceptual reasoning, is shaky.

Chen et al. (2013) sound a caution: everyday memory gaps in DCD disappear once verbal IQ is controlled. The visuospatial deficit is real, but language skills can mask or magnify other scores.

When you see clumsy kids with DCD, expect visuospatial holes on the WISC-IV even if their verbal scores look fine. Don’t chalk up low Perceptual Reasoning to ADHD alone—check for motor signs. Pair cognitive data with motor and academic screens to build a fuller support plan.