Therapygenetics: the 5HTTLPR as a biomarker for response to psychological therapy?

Psychiatric illnesses are under polygenic influence and are associated with interactions between genetic variants and environmental exposures. Gene--environment interactions might not only predict onset of disease, but genetic biomarkers might also help the clinician to select the optimal treatment for patients. However, there is a lack of studies on therapygenetics for psychological treatment of psychiatric diseases. The serotonin transporter gene promoter region (5HTTLPR) in depression and anxiety is particularly of interest, because it is associated with response to stress, and may represent susceptibility to environmental influences. Recently, in this journal, Eley et al. reported preliminary results showing that children with an anxiety disorder carrying the short--short (SS) genotype were significantly more likely to respond to cognitive behavioral therapy (CBT) than those carrying a long allele (SL/LL). The authors state that independent replication is necessary. Moreover, a control group not receiving CBT was lacking and the association did only emerge at follow-up. In an independent sample, using a randomized clinical trial design, we examined whether the short-short allele in recurrently depressed patients was associated with better response to CBT in preventing recurrence compared with a control group.