been reported for example, between internalizing and externalizing phenotypes (see e.g. Rowe et al., 2008). In addition, models of this kind exclude the gene-environment interplay almost certainly involved in risk for externalizing disorders (e.g., Kim-Cohen et al., 2006). At this stage, then, although evidence for genetic associations between CD and ODD is suggestive of shared etiology, it is not sufficient to demonstrate whether they are manifestations of a single disorder.
