Association involving serotonin transporter gene linked polymorphic region and bipolar disorder type 1 in Iranian population

Introduction: Serotonin transporter gene linked polymorphic region, also called 5HTTLPR, is a candidate in the genetics of bipolar disorder; however, the results of previous association studies are inconsistent. Several explanations have been proposed for that inconsistency; among them are the existing differences both in the genetic basis of bipolar disorder subtypes and the genetic backgrounds of the studied populations. We aimed to investigate the association of 5HTTLPR with bipolar disorder type I (BP-1) in Iranian population. Methods: In this case-control study, 146 patients with BP-1 and 165 controls were recruited. The patients were selected through the Structured Clinical Interview for Diagnostic andStatisticalManual ofMentalDisorders, 4th edition. It was required that the patients do not have any present history of general medical conditions, substance abuse, and concurrent major psychiatric disorders. The polymorphism was evaluated by blood sampling and subsequent DNA extraction, polymerase chain reaction, and agarose gel electrophoresis. Chi-square test was used for analyzing allelic and genotype frequencies and two-tailed P values were obtained. Results: The S allele was significantly more frequent in the BP-1 patients compared with the controls (P=0.02, S allele odds ratio=1.5, confidence interval 95%=1.06-2.11). Discussion: Our statistically significant results suggest that the role of 5HTTLPR in the pathogenesis of BP-1 needs to be clarified by further scrutiny in Iranian population and other populations of Near East.