TPH2 and depressive disorder: Some of the most studied TPH2 SNPs related to depression, suicide, and bipolar disorder are: (i) rs7305115 (associated with risk factors for suicide attempts and major depression) [6,7], (ii) rs1386493 (associated with suicide attempts) [8] and (iii) rs4570625 (associated with personality disorders, anxiety, depression, and major depressive disorders) [9,10,11].