Association of serotonin transporter gene polymorphisms and major depressive disorder in Chinese Han population

BACKGROUND： Serotonin transporter （5-HTT） polymorphisms comprise 5-HTT gene-linked polymorphism region （5-HTTLPR） and variable number of tandem repeats （VNTR）. Studies have revealed an association between 5-HTT polymorphism and major depressive disorder, which suggests that the ＂S＂ allele of 5-HTTLPR and Stin2.9 of 5-HTTVNTR are associated with major depressive disorder. However, there are a number of studies that do not support the 5-HTT polymorphism effect in major depressive disorder. OBJECTIVE： To study the relationship between 5-HTT gene polymorphism and major depressive disorder in Chinese Han population. DESIGN, TIME AND SETTING： Case-controlled study of 5-HTT gene polymorphism. The experiment was performed at the Central Laboratory, Third Affiliated Hospital of Sun Yat-sen University, China from March 2005 to January 2006. PARTICIPANTS： A total of 99 depressive patients of Chinese Han nationality were recruited for this study. All patients met DSM-IV diagnostic criteria for major depressive disorder and had a total score of Hamilton Depression Scale （24 items） ≥21 points. In addition, 101 healthy subjects, matched for age and gender, served as the control group. METHODS： Venous blood was collected from all subjects. 5-HTT genotypes and alleles were determined by polymerase chain reaction. Consistent with the Hardy-Weinberg equilibrium, the association between 5-HTT gene polymorphism and major depressive disorder were analyzed by Chi-square test. MAIN OUTCOME MEASURES： 5-HTTLPR and 5-HTTVNTR genotypes and allele frequencies were measured. RESULTS： No significant differences in 5-HTTLPR genotypes and allele frequencies were determined between patients and controls （P 〉 0.05）. However, significant differences in 5-HTTVNTR genotypes and allele frequencies were detected （P 〈 0.01 ）. The Stin2.10 allele and 10/10 genotype associated with major depressive disorder （OR = 2.61,7.7, P 〈 0.05; analysis of dose-response relationships Х^2 = 12.35, P 〈 0.01）. CONCLUSION： Results from the present study revealed no association between 5-HTTLPR and major depressive disorder. However, a significant association between 5-HTTVNTR and major depressive disorder existed in a population of Chinese Han. The presence of Stin2.10 and 10/10 genotypes increased the risk for major depressive disorder in a dose-dependent manner.