Suicidality and 5-Hydroxyindoleacetic Acid Concentration Associated With a Tryptophan Hydroxylase Polymorphism

BACKGROUND: To examine whether the tryptophan hydroxylase (TPH) gene, which codes for the rate-limiting enzyme in the biosynthesis of serotonin, may be a factor influencing serotonin turnover and behaviors controlled by serotonin. METHODS: Using a polymerase chain reaction-based method, TPH genotype was determined in DNA samples from 56 impulsive and 14 nonimpulsive, alcoholic, violent offenders and 20 healthy volunteers. RESULTS: In the behaviorally extreme impulsive group, we observed a significant association between TPH genotype and cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA) concentration. No association of TPH genotype with impulsive behavior was detected. The polymorphism was also associated with a history of suicide attempts in all violent offenders, independent of impulsivity status and cerebrospinal fluid 5-HIAA concentration. CONCLUSION: In some individuals, a genetic variant of the TPH gene may influence 5-HIAA concentration in the cerebrospinal fluid and predisposition to suicidal behavior.