5-HTTLPR

5-HTTLPR (serotonin-transporter-linked promoter region) is a degenerate repeat (redundancy in the genetic code) polymorphic region in SLC6A4, the gene that codes for the serotonin transporter. Since the polymorphism was identified in the middle of the 1990s, it has been extensively investigated, e.g., in connection with neuropsychiatric disorders. A 2006 scientific article stated that "over 300 behavioral, psychiatric, pharmacogenetic and other medical genetics papers" had analyzed the polymorphism. While often discussed as an example of gene-environment interaction, this contention is contested.