5-HTTLPR (serotonin-transporter-linked polymorphic region) is a degenerate repeat polymorphic region in SLC6A4, the gene that codes for the serotonin transporter. It has been extensively investigated in connection with the behavioral, psychiatric, pharmacogenetic aspects of neuropsychiatric disorders.
In contrast to earlier reports, a June 2009 article in JAMA showed no association between 5-HTTLPR genotype and depression.
While many subtypes exist it can be partially genotyped based on rs25531 and rs25532; the minor allele (G) of rs25531 is almost always in phase with the long (L) allele of 5-HTTLPR.[PMID 18055562]
geneticfuture discusses an article; [PMID 19052197] about the genetics of the placebo effect, which associates placebo response with homozygosity of the 5-HTTLPR long allele (and also rs4570625).
blog the effectiveness of placebo treatment for social anxiety disorder may be influenced by this