Serotonin transporter linked polymorphic region in anorexia nervosa and bulimia nervosa

SIR – Strong genetic liability and common etiopathogenetic background have been suggested for Eating Disorders (ED). Several lines of evidence support a possible involvement of serotonin (5-HT) pathways in modulating eating behavior, since alteration in 5-HT activity has been consistently demonstrated in ED. Moreover, 5-HT disturbances seem to persist after recovery. These findings and the efficacy of 5-HT reuptake inhibitors in the treatment of ED suggest the serotonin transporter (5-HTT) gene as a good candidate for genetic studies. A deletion (short variant = s)/insertion (long variant = l) functional polymorphism has been described within the promoter region of the 5-HTT gene (5-HTTLPR). Studies of transfected cells in culture show that the long and short variants exhibit different transcriptional properties. In particular, basal transcriptional activity of the long variant is more than twice that of the short form. We studied this polymorphism in a sample of 50 bulimic (BN), 56 anorexic (AN) patients (19 restricting and 37 binge-eating type) and 120 healthy controls, closely questioned to exclude any psychiatric disorder. Informed consent was obtained from all the subjects, females, unrelated and of Italian descent. Patients fulfilled DSM-IV diagnostic criteria and were sequentially recruited at the Eating Disorder Clinic and Research Unit at San Raffaele University Hospital, Milan. Genomic DNA was extracted from whole blood and the polymorphism was analyzed as previously described. Statistical analysis was performed with x statistics and power calculation with the EPINFO program (version 6.04b, 1997). Table 1 shows the distribution of 5-HTTLPR alleles and genotypes in our sample. Genotype frequencies in controls and both subtypes of AN patients are in Hardy–Weinberg (H–W) equilibrium, while the BN group shows a significant deviation due to a lowerthan-expected frequency of the l/l genotype.