Oppositionality and delinquency seemed to be the most important behavioural phenotypes in explaining the heritability of all our environmental variables—displaying genetic correlations with each (although it is noteworthy that the genetic correlation between oppositionality and delinquency was almost perfect in every model). Depression was related to maternal negativity and negative life events, with anxiety and physical aggression being genetically related to one environmental variable each. It is intriguing that physical aggression, being a serious problem behaviour, was only weakly related to maternal/paternal negativity and not genetically correlated at all. This could be attributed to the artefactual effects of using a sample displaying only low levels of physical aggression. However aggression was genetically correlated with negative life events, thus physical aggression may in fact not be genetically related to parental negativity at all.
