The Association of 5-HTTLPR Gene Polymorphisms and Eating Disorder: A Meta-Analysis

Background: Eating disorders (EDs), are characterized by abnormal eating habits, including insufficient or excessive food intake, and are detrimental to an individual’s physical and mental health. In this paper, we focus on AN (anorexia nervosa) and BN (bulimia nervosa), which are included in EDs. Some studies reported that there may be an association of 5-HTTLPR gene and eating disorders but without clear conclusion to solidify this relationship. Therefore, the goal of this study is to summarize on the reported data and meta-analytically investigate the relationship between the 5-HTTLPR gene polymorphisms and eating disorders. Method: We searched through all published papers indexed in MEDLINE, EMBASE, and CNKI from inception to May 2015. All studies that we examined regarding the relationship between 5-HTTLPR polymorphisms and EDs were identified to perform this meta-analysis. Odds ratio (OR) and 95% confidence intervals (CIs) were used to evaluate the EDs risk. Results: Fourteen studies met the inclusion criteria. We performed this meta-analysis involving 2238 subjects in total (including 1832 EDs patients, 779 AN patients, 722 BN patients and 406 control subjects). The 5-HTTLPR S allele was significantly more common in all EDs patients comparing to controls (S vs. L allele: OR=1.25, 95% CI: 1.021.53, P=0.03). This significance was also revealed through the recessive model (SS vs. SL+LL: P=0.008) and the additive model (SS vs. LL: P=0.03). When the comparison was stratified by ethnicity (Caucasian and Asian), it shows that the significance only exists in recessive model among Caucasian population (P=0.03). Subsequently, the EDs patients were divided into two groups (AN and BN) to analyze the association between 5-HTTLPR polymorphism and AN or BN. The results showed that S allele was significantly more frequently discovered in the AN group than in the control group (P=0.006). Other comparison models suggest similar results. Ethnically stratified analysis suggested that 5-HTTLPR polymorphism only correlates with AN among Caucasians, but not Asians. However, no statistical difference was found between BN patients and controls in any comparative analysis. Conclusion: The 5-HTTLPR S allele can result in increased risk for AN but not BN. Of all the ethnical groups that we studied, Caucasian females appear to be the most likely to become susceptible to EDs/AN under the influence of 5-HTTLPR S allele. These results may be helpful to our clinical practice. However, further studies with larger sample sizes are needed for more reliable and conclusive results.