Table 1.

Polymorphisms associated with serotonin and melatonin signaling and their predicted effects.

Gene	Product	Polymorphism	Effect
SLC6A4	Serotonin transporter	L (long) and S (short) allele	L allele is associated with elevated transcription of the gene and reduced serotonin signaling.
HTR1F	Serotonin receptor		Associated with migraines.
NAT2	N-acetyl transferase 2		Associated with prostate cancer susceptibility of AAs.
TPH1	Tryptophan hydroxylase (Gut)	A218C	A allele is associated with borderline personality disorder due to serotonergic dysfunction [51].
TPH2	Tryptophan hydroxylase (Enteric neurons)	rs4290270; rs4570625; rs41317118; rs11178998; rs7305115; rs17110747; rs10748185; rs18438099; rs11316791; rs1386493; rs1386494	rs4290270 (A/T allele) could be associated with major depressive disorder [52].