The relationship between ADHD symptoms and mild intellectual disability (ID) was investigated and compared to subjects with average ability, in a study at King’s College London, Institute of Psychiatry, UK. In a total of 192 subjects included in the analysis, there was a negative linear relationship between ADHD symptoms and IQ (P<0.001). ADHD symptoms are increased in children with ID, and the mean IQ of children with hyperkinetic disorder is 15 to 16 points below those without hyperactivity. The findings were not explained by inappropriate rater expectations or comorbidity with emotional/behavioral problems. 
COMMENT. ADHD is likely to be more common in children with mild intellectual disability.