"Diminished" association between the serotonin transporter linked polymorphism (5HTTLPR) and body mass index in a large psychiatric sample

Background: The role of the promoter polymorphism (51-ITTLPR) of the serotonin transporter gene (SLC6A4) in psychiatric illnesses has been studied extensively. Serotonergic function also regulates many central nervous system, including appetite and feeding behaviors. The 5HEFLPR short allele was found to be associated with increased body mass index and obesity risk among the general population. No data is available to support generalizability of such association among psychiatric population. Methods: We examined the relationship between BMI and the 5HEFLPR genotype in a large sample of 1831 psychiatric patients at Mayo Clinic, Rochester, Minnesota, using a retrospective chart review. Results: Average BMI among groups with the short!short (2829 - 727 kgm²), the shortlong (2807 - 645 kgm²) and the longlong (2815 - 751 kgm2) genotypes of 5HEFLPR were not statistically different. This negative association persisted even with the sub-analysis of the Caucasians. However, we observed an increased rate of obesity among our psychiatric patient sample compared to the general population of Minnesota (366% versus 276%, p=0000l for males, 303% versus 244%, p=00001 for females). Also, sub-analysis showed female inpatients to have a significantly higher average BMI than outpatients (2864- 808 kgm2 versus 2713 - 692 kgm2, p=0026). This confirmed a significant association between mental health disorder and BMI. Limitations: Retrospective study design with limited control for potential confounders. Conclusions: In this large sample of psychiatric patients we found no significant association between 5HEFLPR genotype and BMI, which is different from the case with general population reported in the literature.