Genetic variability in tryptophan hydroxylase 2 gene in alcohol dependence and alcohol-related psychopathological symptoms

Heritability plays an important role in the development and expression of alcohol dependence. The present genetic association study explored the role of TPH2 polymorphisms and their haplotypes to investigate its role in alcohol dependence and comorbid psychopathological symptoms. The sample included 101 subjects currently diagnosed as alcohol abusers, 100 abstinent alcohol-dependent subjects and 97 healthy controls. Subjects were genotyped for TPH2 rs4570625, rs1843809, rs7305115, rs4290270. TPH2 genotypes were not associated with alcohol dependence, but GGAA haplotype was less common (p = 0.038) and GTAA and GGGT were more common (p =0.011 and p=. 0.021, respectively), in currently dependent patients compared to controls. Exploratory analysis of genotypes in currently dependent patients showed that rs1843809 was associated with depressive and aggressive traits (p = 0.045 and p = 0.001, respectively), rs4290270 with depressive and anxiety traits ( p = 0.040 and p= 0.025, respectively) and rs4570625 with aggressive traits ( p = 0.011). In abstinent subjects rs1843809 genotype was associated with traits of social anxiety (p =0.003). Only association between rs1843809 and the BDHI score (p = 0.001) and associations between GTAA haplotype and Zung Anxiety Scale and BDHI score ( p = 0.001 and p< 0.001, respectively), in currently dependent patients remained significant after applying the Bonferroni's correction.Our findings support a potential role of TPH2 in alcohol dependence. TPH2 genetic variability may be also associated with anxiety and aggression traits in alcohol dependent subjects.