Is there a link between Depressive Disorders and Tryptophan Hydroxylase 1 (TPH1) Gene Polymorphism? - Study from a Distressed Area, Kashmir (India)

BACKGROUND: The progress that man has made in all domains of life, during all these years of reign over the earth, is utterly remarkable. However, it always came at a price. Each epoch of progress has seen human beings inflicted with trauma and cynical consequences. During the last two decades, Kashmiri (Indian) people have experienced continuous violence, a reign of terror, and political turmoil. Each of these disastrous events has contributed to the increase in psychiatric disorders in this part of the world, especially major depressive disorders. We can observe that besides the environmental influences, gene polymorphism also plays a crucial role in the development of depressive disorders. The role of Tryptophan Hydroxylase 1 (TPH1) gene is implicated in various psychiatric disorders, including depression. However, no study has investigated TPH1 A779C gene polymorphism in depressive disorders in a distressed society like Kashmir (India). AIMS: To study TPH1 A779C single nucleotide polymorphism in depressive disorders in Kashmiri (Indian) population. MATERIALS AND METHODS: Two hundred and forty patients diagnosed with depressive disorder, and 160 unrelated healthy volunteers (control), were studied in a case-control study design. Polymorphism was determined using polymerase chain reaction (PCR) and agarose gel electrophoresis, after digestion with HAP II enzyme. Genotypes and allele frequencies were compared using Chi-square tests, Fisher’s exact test, odds ratio, 95% confidence interval (C.I.) and a p-value of <0.05 was considered to be statistically significant. RESULTS: The mean age ± standard deviation (SD) of depression and control group was 32.02±10.99 and 31.75±9.93, respectively (p= 0.512). It was found that the patients from depression group had AA genotype (51.7%) in comparison to control group (17.5%) and these results were statistically significant (p≤0.0001). Calculation of allelic frequency revealed a stronger association of A allele with depression group (70.83%) than with the control group (41.25%), and it was also found to be statistically significant (p≤0.0001) with C.I. of 3.459 (1.909-6.266). CONCLUSION: TPH1 A779C A gene was found to be associated with a major depressive disorder (MDD) in Kashmiri (Indian) population. There were high HAM-A as well as HAM-D scores in depressive patients of Kashmir (India).