Lack of association between the tryptophan hydroxylase gene A218C polymorphism and attention-deficit hyperactivity disorder in Chinese Han population

Previous studies have suggested that the serotonergic (5-HT) system might b e involved in the development of Attention-deficit hyperactivity disorder ( ADHD). ADHD is frequently characterized by aggressive and impulsive behavio r, a major symptom associated with reduction in serotonergic function. The tryptophan hydroxylase (TPH) gene is a reasonable candidate for ADHD becaus e it encodes the rate-limiting enzyme in the process of 5-HT biosynthesis. In this study, we examined the relationship between the A218C polymorphism in TPH gene and ADHD. Sixty-nine ADHD patients and their biological parents were investigated. The A218C polymorphism in intron 7 of TPH gene was dete cted by PCR-RFLP method. No allele or genotype concerned with this A218C po lymorphism was found to be associated with ADHD when analyzed with the hapl otype relative risk method. Therefore, our data indicate that the TPH gene A218C polymorphism may not be a susceptibility factor of ADHD in the Chines e Han population. (C) 2001 Wiley-Liss, Inc.