Background: Despite its effectiveness, there are still many concerns and questions about the principles and therapeutic methods of Traditional Medicine (TM). In other words, to accept TM as a reliable healthcare system, modern scientific research should approve the principles of this system. Temperament is one of the major determinants of Persian Medicine (PM), which is practically utilized to diagnose and cure diseases. Considering the association of depression with the coldness temperament and the serotonin-Tansporter-Linked Promoter Region (5-HTTLPR) polymorphism, we proposed that the serotonin transporter gene could be one of the candidate genes contributing to the specification of temperament. To test this hypothesis, we examined the association of 5-HTTLPR polymorphism with the hot/cold status of temperament in healthy individuals.

Materials and Methods: The study included 351 healthy men (aged 20-40 years) referred to the organization of blood transfusion in Shiraz City, southern Iran. The participants’ temperament (warm, temperate, and cold) was determined using a standard self-reported scale. Then, we performed Polymerase Chain Reaction (PCR) to determine their 5-HTTLPR polymorphism genotype. Multinomial logistic regression was used to evaluate a 95% CI and odds ratios for the association of temperament with the 5-HTTLPR genotypes. Statistical analysis was performed using the SPSS at a significance level of less than 0.05.

Results: Regarding the warm temperament, no association with the 5-HTTLPR genotypes was observed. However, regarding cold temperament, although our data showed no association with the SS, the LS genotype showed some association. With reference to LL, the LS genotype decreased the possibility of coldness rather than temperateness for the temperament (OR=0.471, P=0.040).
Conclusion: Our data revealed the association of temperament with the 5-HTTLPR polymorphism, suggesting that the serotonergic system may influence temperament. Further studies are required to explore the relation of genetic factors with temperament.