Childhood-onset schizophrenia and tryptophan hydroxylase gene polymorphism.

We explored the relationship between the tryptophan hydroxylase gene polymorphism and susceptibility to childhood-onset schizophrenia in a Japanese sample. Subjects were 51 Japanese patients who met DSM-IV criteria for schizophrenia before age 16 and 148 Japanese healthy controls. DNA was extracted from whole blood and genotyping was performed by PCR-RFLP using Nhe I. The frequency of the A allele was relatively higher in patients with childhood-onset schizophrenia than in controls (odds ratio, OR = 1.47, 95% CI = 0.97-2.37, P = 0.097). There was a nearly doubling of the risk for childhood-onset schizophrenia associated with the AA genotype compared to other genotype groups; OR = 1.97, 95% CI = 0.91-4.22, P = 0.058.