Preliminary Evidence of the Short Allele of the Serotonin Transporter Gene Predicting Poor Response to Cognitive Behavior Therapy in Posttraumatic Stress Disorder

Objective This study was intended to assess the extent to which the low-expression alleles of the serotonin transporter gene promoter predict poor response to cognitive behavior therapy in patients with posttraumatic stress disorder (PTSD). Method Forty-five patients with PTSD underwent an 8-week exposure-based cognitive behavior therapy program and provided mouth swabs or saliva samples to extract genomic DNA and classify individuals according to four allelic forms (SA , SG , LA , LG ) of the 5-HTT-linked polymorphic region (5-HTTLPR). We determined whether the 5-HTTLPR genotype predicted change in PTSD severity following treatment ( n = 45) and 6 months later ( n = 42). Results After controlling for pretreatment PTSD severity and number of treatment sessions, the 5-HTTLPR low-expression genotype group (S or LG allele carriers) displayed more severe PTSD 6 months following treatment relative to other patients. Conclusions This study suggests a genetic contribution to treatment outcome following cognitive behavior therapy and implicates the serotonergic system in response to exposure-based treatments in PTSD.