Letter: serotonin transporter gene polymorphisms and the irritable bowel syndrome

We read with interest the article by van Kerkhoven et al. reporting the association between a functional polymorphism in the gene encoding for activity of the serotonin transporter protein and the irritable bowel syndrome (IBS).1 The authors concluded that a genetic polymorphism in the gene encoding for activity of the serotonin transporter protein is not associated with IBS. There have been several studies about the serotonin transporter (SERT) gene polymorphism and IBS published after this study.2-7 We performed a meta-analysis to assess the association between the SERT gene polymorphism and IBS subtype. The association between SERT-P (L/L, L/S, S/S) gene polymorphism and IBS was compared using the odds ratio (OR) and 95% confidence interval (CI). In the complete population, there was no significant association between the SERT-P (L/L) gene [OR = 0.98 (95% CI = 0.66–1.46), P = 0.94], (L/S) gene [OR = 0.95 (95% CI = 0.73–1.25), P = 0.73], (S/S) gene [OR = 1.21 (95% CI = 0.84–1.75), P = 0.31] and IBS. In the subgroup analyses by IBS subtypes, there was a significant association between the SERT-P (L/L) [OR = 1.52 (95% CI = 1.15–2.01), P = 0.003] and IBS with constipation (C-IBS) (Figure 1). There was no significant association between the SERT-P (L/L, L/S, S/S) gene and IBS with diarrhoea (D-IBS) or mixed IBS (M-IBS). Our meta-analysis showed that there is an association between the genetic polymorphism in the SERT-P gene (L/L) and C-IBS. As colonic motility and secretion is far more complicated than the genotype and polymorphisms discussed here the local 5-HT content, the 5-HT receptor, the harmonious enteric nerve reflexes, and the 5-HT receptor agonist might also play a role. Declaration of personal and funding interests: None.