No association between the tryptophan hydroxylase gene polymorphism and major depressive disorders and antidepressant response in a Korean population

The serotonergic neurotransmitter system has been implicated in major depressive disorder (MDD) and appears to be the target of a variety of antidepressants. Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin biosynthesis, and selective serotonin re-uptake inhibitors exert their activity enhancing the general serotonergic tone. The goal of this study was to investigate whether the A218C polymorphism of the TPH gene is associated with MDD or antidepressant response. All patients were evaluated at the start and in the eighth week of using the 21-item Hamilton Depression Rating Scale. Genotyping was analyzed with polymerase chain reaction. There were no significant differences in genotypes and allele frequencies between the MDD patients (n=93) and the control group (n=127) and in the antidepressant response among TPH gene variants. Results suggest that the A218C polymorphism of the TPH gene does not play a major role in pathogenesis in MDD and does not serve as a modulator of antidepressant activity.