[Practical executive function performance in high intelligence quotient children and adolescents with...

To explore the practical executive function profiles in high IQ (intelligence quotient) children and adolescents with attention deficit hyperactivity disorder (ADHD) in a Chinese sample population.

For this cross-sectional study, we identified 124 outpatients aged 6.8 - 13.1 years with a high IQ fulfilling the diagnostic criteria for ADHD according to the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV), 68 children and adolescents without ADHD aged 6.5 - 13.1 years with a high IQ matched by high IQ children and adolescents with ADHD, 124 outpatients aged 6.8 - 13.2 years with an average IQ with ADHD and 68 normal children and adolescents aged 6.4 - 13.1 years with an average IQ matched by IQ. We operationalized high IQ as having a full scale intelligence quotient (IQ or FSIQ) ≥ 120 on Chinese version Wechsler intelligence scale for children (C-WISC) and an average IQ as 90 ≤ IQ < 110. All the above groups were matched by age. All subjects completed practical executive function tests, including Stroop color-word, trail-making, digit span, Tower of Hanoi task and verbal fluency to assess their ability in the aspects of inhibition, shifting, working memory, planning and verbal fluency.

ADHD group with a high IQ performed worse on the Stroop color-word (3.18 ± 0.05) and trail-making tests (4.38 ± 0.55) than normal control group with a high IQ (2.92 ± 0.07 and 4.05 ± 0.07) (P < 0.01). The test performances of trail-making, digit span (4.86 ± 0.13) and fluency (23.0 ± 0.5) were significantly better in high IQ ADHD group than average IQ ADHD group (4.10 ± 0.07 and 19.9 ± 0.5) (P < 0.01).

Though a bit better than average IQ ADHD group in shifting, working memory and verbal fluency, the high IQ children and adolescents with ADHD perform worse than high-IQ controls on inhibition and shifting. IQ may protect practical executive function.