Attention deficit hyperactivity disorder (ADHD) is a severe behavioral disorder in children known to have a substantial genetic component. Prior studies have implicated serotonin genes in the etiology of ADHD but have not examined tryptophan hydroxylase (TPH), which is a rate-limiting enzyme in serotonin biosynthesis. The current study examined the relationship between the A218C and A-6526G polymorphisms of the TPH gene and ADHD. Three hundred sixty-two unrelated ADHD probands and their biological parents were recruited to participate in this study. No biased transmission of any allele of the two polymorphisms was observed using TDT analysis. However, haplotype analyses found that the rare 218A/-6526G haplotype was significantly not transmitted to probands with ADHD (chi(2) = 4.4995, P = 0.034), regardless of subtype. Although this finding for ADHD in the Chinese Han population.
(c) 2006 Wiley-Liss, Inc.