Tryptophan hydroxylase polymorphisms in suicide victims

Both environmental and genetic factors appear to contribute to the risk for suicide. The serotonergic system has been implicated in depression, impulsivity and suicidality. Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of serotonin. Suicide has been associated with polymorphisms in intron 7 of the TPH gene. These alleles were studied in samples from 47 deceased Caucasian males as part of the Utah Youth Suicide Study. A 918 base pair fragment spanning the region of interest was amplified. The A218C polymorphism was visualized by restriction fragment length polymorphism (RFLP) and the A779C was sequenced. Neither A218C nor A779C appeared to be associated with suicide in this population. These results did not change when the sample was stratified by age (10-21 years, 22-31 years) or when violent suicides were selected. The complexity of the phenotype of suicide may reflect multiple biological and social etiologic factors, and poses a worthy challenge for genetic studies.