Results: At baseline, scores were not statistically different between the 2 groups. After 6 months, PIQ and FSIQ scores of intervention group were higher than those of the control group (P < 0.05). Compared with baseline scores, the intervention group, but not the control group, showed significant increases in Verbal IQ (P < 0.05), PIQ (P < 0.01), and FSIQ (P < 0.01). In the intervention group, the 5 subtests scores of PIQ improved significantly (P < 0.01). In the control group, none of the scores from the subtests showed statistical differences. Furthermore, there was no statistical difference between the change of IQ scores and children's age, sex, different subtypes of ADHD, and drug dosage.
Conclusions: Methylphenidate can enhance cognitive performance in ADHD patients thus evaluating their IQ scores, although the effect size seems to be relatively small. The result should not be indicated as an increase in intelligence.