Tryptophan hydroxylase gene 1 polymorphisms are not associated with suicide attempts in alcohol-dependent individuals.

A serotonergic dysfunction was suggested to be involved into the biological susceptibility of suicidal behaviour. Tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin biosynthesis, is a significant regulating factor in the serotonergic system. Recently the A-6526G, and G-5806T and A-779C polymorphisms of the TPH 1 gene were identified and suggested to be associated with suicidal behaviour, but study results are conflicting. We examined a possible association of the A-6526G, and G-5806T and A-779C polymorphisms with suicide attempts in a sample of 80 alcohol-dependent individuals with a history of at least one suicide attempt. This group was analysed in comparison with 241 alcohol-dependent subjects without such a history. No significant relationship between haplotype and genotype distribution and allele frequencies of these polymorphisms with suicide attempts were detected. Furthermore, no association with number of suicide attempts and TPH haplotypes were found. Our data do not support the hypothesis of A-6526G, G-5806T or A-779C polymorphisms to be associated with suicide attempts in alcohol-dependent individuals.