Objective: To investigate the features of cognitive function in children with attention deficit/hyperactivity disorder (ADHD).
Methods: Wechsler Intelligence Scale for Children-RC, Wechsler Memory Scale (WMS), Number Cancellation Test, Ravin's Standard Progressive Matrices, and Stroop test were conducted among 60 7 approximately 12-year-old children diagnosed with ADHD and 60 children matched by age, sex, and maternal education level.
Results: The verbal intelligence quotient, performance IQ, full scale IQ, verbal comprehension IQ, perceptual organization IQ, and freedom from distractibility IQ of the ADHD CHILDREN were 104 +/- 13, 98 +/- 14, 102 +/- 13, 100 +/- 15, and 102 +/- 15, all less than those of the controls (112 +/- 11, 108 +/- 13, 112 +/- 12, 111 +/- 12, 107 +/- 13, and 116 +/- 13, all P < 0.01). The scores of long-term memory, short-term memory, immediate memory, memory quotient, and reverse digit span in the children with ADHD were 40 +/- 7, 58 +/- 12, 7 +/- 3, 95 +/- 15, and 4.2 +/- 1.7 respectively, all less than those in the controls (49 +/- 5, 63 +/- 10, 8.4 +/- 3.0, 109 +/- 12.5, and 5.0 +/- 1.4 respectively, all P < 0.05). Number cancellation test showed significantly lower total score and higher error rate in ADHD children than in the controls (51.5 and 76.4 VS 77.3 and 38.0, both P = 0.000). In Stroop test, the ADHD children spent more time for all the four parts, had to make more effort to eliminate the interference of word meaning, and made more errors in the C and D parts. The average standard score of Raven's Standard Progressive Matrices was 4.0 +/- 1.5, significantly higher than that in the controls (2.7 +/- 1.2, P = 0.000).
Conclusion: The levels of intelligence, memory, and attention in ADHD children are lower that those in normal children. ADHD children have deficiency in executive functions, such as selective inhibition, working memory and plan implementation.