Since the heritability estimate in twin design includes variation due to interactions between genes and shared environment (Uher, 2008, 2009), and since experiences of maltreatment are often shared by siblings growing up in the same family (Brown et al., 2007; Jaffee et al., 2007), the possibility is raised that G×E of the type reported here could contribute to the observed heritability of persistent or recurrent depression. The present findings also underscore the public-health relevance of G×E, as persistent forms of depression are responsible for most disability, health-care costs and risk of suicide (Greenberg et al., 2003; Young et al., 2008).
