There is a reason to believe that suicidal behavior has a genetic component independent of the risk imposed by psychiatric
disorders such as alcoholism, bipolar disorder, and depression. Some candidate genes in this domain have also been identified—for
example, the serotonin transporter gene, the tryptophan hydroxylase genes, and hypothalamus-pituitary-adrenal axis genes such
as BDNF, NTRK2, and SSAT.