Introduction: Numerous association studies of candidate genes studies with major depressive disorder (MDD) have been conducted for many years; however, the evidence of association between genes and the risk of developing MDD still remains inconclusive. In this study, we aimed to investigate the association between the tryptophan hydroxylase 2 (TPH2) gene and MDD in three ethnic groups (Malay, Chinese and Indian) within the Malaysian population.
Methods: Two hundred and sixty five MDD patients who fulfilled the Diagnostic and Statistical Manual of Mental Disorders-IV criteria for MDD and 332 healthy controls were recruited for the study. All cases and controls were then genotyped for TPH2 polymorphisms rs1386494, rs1386495 and rs7305115.
Results: Single locus analysis in pooled and ethnically stratified subjects revealed no association between each of the three variants of the TPH2 gene with susceptibility to MDD. Strong linkage disequilibrium was detected between rs1386495 and rs1386494 in pooled subjects; however, no significant association was found in the haplotype analysis.
Discussions: In this study, we suggest that in both the Chinese and Indian populations, gender distribution differ significantly between cases and controls, showing that women are more at risk of developing MDD compared with men. Therefore, we suggest that the occurrence of MDD in both Chinese and Indians in the Malaysian population may be influenced by gender.
Keywords: major depressive disorder; polymorphism; serotonin; tryptophan hydroxylase gene 2.
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