One source of discrepant results may be cross-study inconsistency in the measurement of depression. While the liability to developing depression resulting from childhood maltreatment is life-long, the manifestations of depression are often episodic and their duration and course vary between individuals (Eaton et al., 2008; Judd, 1997; Rhebergen et al., 2009; Solomon et al., 1997). Chronic or recurrent depression is more heritable (Foley et al., 1998; McGuffin et al., 1996) and is more strongly associated with childhood maltreatment (Wiersma et al., 2009) than depression diagnosed at a single time point. Moreover, the influence of childhood maltreatment on depression persistence is direct and cannot be accounted for by more proximal circumstances (Brown et al., 2008). These observations led Brown and Harris (2008) to hypothesize that genetic sensitivity to childhood maltreatment should be specific to depression that is chronic or recurrent.
