No association between catechol-O-methyltransferase (COMT) genotype and attention deficit hyperactivity disorder (ADHD) in Japanese children

Objective: This study ascertained the association between attention deficit/hyperactivity disorder (ADHD) in Japanese children and a polymorphism of catechol-O-methyltransferase (COMT), a dopamine-control gene. The secondary aim of the study was the evaluation of a putative association between methylphenidate (MPH) effect/adverse effects and the COMT genotype. Methods: To ascertain the distribution of the Val158Met variant of COMT, 50 children meeting ADHD inclusion criteria were compared with 32 healthy children. Clinical improvement and the occurrence of adverse effects were measured before and 3 months after MPH administration in children with ADHD, and analyzed for genotype association. Wechsler Intelligence Scale for Children-Third Edition (WISC-III), age, MPH dose were included as co-variables. Results: The occurrence of the COMT Val/Val genotype was significantly higher in children with ADHD (χ2(1) = 7.13, p < 0.01). However, there was no significant difference in the Val/Val genotype according to disorder, and WISC and ADHD rating scale scores, after correcting for the interaction between disorder and COMT genotype. Furthermore, no significant difference in MPH effect/adverse effects was observed in association with the COMT genotype in the ADHD group. Conclusions: These results showed a lack of association between the COMT Val/Val genotype and ADHD in Japan.