The present study extends previous knowledge about the interplay between the serotonin transporter gene and childhood maltreatment in the causation of adult depression, in two ways. First, it finds support for the hypothesis that the interaction between the short allele of 5-HTTLPR and childhood maltreatment is specific to depression that runs a persistent course (Brown and Harris, 2008). In two longitudinal cohorts, the interaction between 5-HTTLPR and childhood maltreatment significantly affected the risk of persistent depression but had no effect on time-limited single-episode depression. Second, it suggests that the longitudinal characterization of the clinical course of a disorder may improve the reliability of testing G×E. While analyses of depression phenotypes based on repeated assessments provided consistent evidence of G×E, analyses based on single cross-sectional assessments yielded inconsistent results. These two findings have broader implications for etiological research.
