The present article reports the first test of this hypothesis. Because retrospective assessment of depression is unreliable (Moffitt et al., 2010; Schraedley et al., 2002), a valid test requires longitudinal datasets with repeated assessments. We use data from two population-based cohorts, where depression was assessed on four separate occasions in adulthood with the same diagnostic instrument. The first cohort provides analyses of new data from the Dunedin longitudinal study and the second cohort offers an opportunity to replicate findings in a new dataset. We examine genetic sensitivity to childhood maltreatment in relation to (a) persistent depression, (b) single-episode depression and (c) past-year depression diagnosed at each of the four separate assessment occasions. Comparisons of G×E results for single-episode versus persistent depression test the hypothesis proposed by Brown and Harris (2008). Analyses of past-year depression are comparable to G×E studies that have focused on cross-sectional measurements rather than longitudinal phenotypes. Comparisons of G×E results for depression diagnosed on any given occasion versus persistent depression allow us to gauge the possible contribution of cross-sectional measurement to inconsistencies in the literature.
