Polymorphism of the serotonin transporter gene (5-HTTLPR) in major depressive disorder patients in Malaysia

Introduction The serotonin transporter promoter (5-HTTLPR) is a potential susceptibility locus in the pathogenesis of major depressive disorder. However, data from Malaysia is lacking. The present study aimed to determine the association between the homozygous short variant of the serotonin transporter promoter gene (5-HTTLPR) with major depressive disorder. Methods This is a candidate gene case-control association study. The sample consists of 55 major depressive disorder probands and 66 controls. They were Malaysian descents and were unrelated. The Axis I diagnosis was determined using Mini International Neuropsychiatric Interview (M.I.N.I.). The control group comprised healthy volunteers without personal psychiatric history and family history of mood disorders. Participants' blood was sent to the Institute Medical Research for genotyping. Results The present study failed to detect an association between 5-HTTLPR ss genotype with major depressive disorder (?2?=?3.67, d.f.?=?1, P?=?0.055, odds ratio 0.25, 95% confidence interval?=?0.07-1.94). Sub-analysis revealed that the frequency of l allele in healthy controls was higher (78.0%) than that of Caucasian and East Asian population. However, in view of the small sample size this study may be prone to type II error (and type I error). Discussion This preliminary study suggests that the homozygous short variant of the 5-HTTLPR did not appear to be a risk factor for increasing susceptibility to major depressive disorder.