The relationship between SLC6A4 gene 5-HTTLPR polymorphism with early childhood maltreatment and parenting perceptions in major depressive disorder

The aim of this research is to detect 5-HTTLPR polymorphism in Major Depressive Disorder (MDD) patients and healthy volunteers; to investigate the interaction between early childhood maltreatment, parenting perceptions and 5-HTTLPR polymorphism and to explore new findings about the role of gene-enviroment interaction on the onset of MDD, its severity and reccurency. Participants consisted of patients and healthy volunteers at the Outpatient Psychiatry Clinic of Başkent University Ankara Hospital. Diagnosis of MDD was ascertained using the Composite International Diagnostic Interview (CIDI) to all patients and healthy volunteers, 99 patients with MDD diagnosis were included to the study. One hundred and eight healthy volunteers who had no psychiatric illness according to CIDI were included. The Sociodemographic and Clinical Data Form, Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Young Parenting Inventory (YPI) and Childhood Trauma Questionnaire (CTQ) have been applied to all participants. The 5-HTTLPR polymorphism at SLC6A4 has been genotyped in all participants. There was no genotype distribution difference between patient and control groups, and also there was no significant difference between the two groups' BDI and BAI scores if only genotype was considered. However the CTQ and YPI scores were significantly higher in the MDD group with respect to the control group. Analysis in a regression model revealed that high CTQ and YPI scores yield to high BDI and BAI scores within all participants. Correlation analysis revealed that carriers with one or two copies of the S allel have higher CTQ and YPI scores than healthy volunteers. Although patients with L/L genotype also had significantly higher CTQ and YPI scores in some subscales than healthy volunteers, this difference was not as distinct as in S allel carriers. In this study, we have used early childhood traumatic experiences and perceived parenting qualities to explore the gene-environment interaction on the onset of MDD. Although our findings indicate that early environmental factors are very effective in MDD development, the carriers of the S allel seem to be more susceptible to early stressful events compared to individuals who have L/L genotype. Only having the risky genotype determines neither the onset nor the severity of MDD. Keywords: 5-HTTLPR, depression, chilhood maltreatment, parenting