TPH1 is associated with major depressive disorder but not with SSRI/SNRI response in Taiwanese patients

Rationale Tryptophan hydroxylase 1 (TPH1), which encodes the rate-limiting enzyme tryptophan hydroxylase in the biosynthesis of serotonin, is a candidate gene in the development and treatment response of major depressive disorder (MDD); however, its actual role is uncertain.