We turn next to discuss developments in the field of gene by environment interaction, focusing on publications involving the serotonin transporter. For those unfamiliar with this story, a brief reminder that the most highly cited paper in neuroscience in 2003 was the observation from a longitudinal study that possession of the ‘short’ allele of the 5-HTTLPR only increased the risk of developing depression in the presence of adverse life events [20]. This is an example of a gene by environment interaction (G × E), which opened the door to detecting many more such effects in studies that measured both environmental and genetic predisposition. While quantitative genetic studies indicated strongly that G × E existed in aggregate [21], this was the first demonstration that it could be detected at a single locus.
