Objective: 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.
Methods: 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.
Results: 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).
Conclusion: 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.