Excess Tryptophan Hydroxylase 17 779C Allele in Surviving Cotwins of Monozygotic Twin Suicide Victims

24 surviving Swedish monozygotic twins whose monozygotic cotwins had completed suicide were compared to 158 demographically sampled Swedish general population controls for tryptophan hydroxylase (TPH) alleles. Serotonin transporter alleles were also examined. The living monozygotic cotwins of suicide victims had a significantly higher TPH 17 779C allele frequency than controls. No significant difference was observed for serotonin transporter alleles. Further studies in larger samples are needed. (27 refs.)