Meta-analysis: a functional polymorphism in the gene encoding for activity of the serotonin transporter protein is not associated with the irritable bowel syndrome

Background Serotonin is associated with symptoms of the irritable bowel syndrome, its action is terminated by the serotonin transporter protein. Aim To assess the association between a functional polymorphism in the gene encoding for activity of the serotonin transporter protein and the irritable bowel syndrome. Methods Meta-analysis of studies identified through a Medline, PubMed and Web of Science search, describing the prevalence of a polymorphism in the serotonin transporter gene creating long and short alleles. Results Eight eligible studies described a total of 1034 patients with the irritable bowel syndrome, and 1377 healthy controls. Presence of the short allele is not associated with an increased risk for the irritable bowel syndrome: OR 1.0; 95% CI: 0.7-1.4 for homozygous subjects, and OR 1.0; 95% CI: 0.8-1.2 for homozygous subjects and heterozygotes together. Although Caucasians and Asians had diverging genotypic frequencies, no association with the shot allele and irritable bowel syndrome was observed in subgroups: Asians OR 1.2; 95% CI: 0.9-1.6 and OR 1.1; 95% CI: 0.2-5.9; Caucasians OR 0.9; 95% CI: 0.5-1.7 and OR 0.9; 95% CI: 0.7-1.2, respectively, for homozygous subjects alone and for homozygous subjects and heterozygotes together. Conclusion A genetic polymorphism in the gene encoding for activity of the serotonin transporter protein is not associated with the irritable bowel.