Serotonin transporter plays an important role in serotogenic transmisssion and the serotonin transporter gene is under investigation in connection with many psychiatric disorders. There are two main genetic variations in the promoter region of the gene - long (L) allele and a short (S).
The S allele is associated with decreased transcriptional efficiency of the promoter leads to reduced serotonin re-uptake in comparison to the long allele which is associated with greater gene expression. The length of polymorphisms are considered to be important mediators of emotional instability and predisposition to mental illness, high trait anxiety, fear-related behavior, negative emotions.
The serotonin transporter gene has received much attention in association with psychiatric disorders and its explication can improve understanding to its principles.