Similar patterns were found when results were examined separately for males and females, and a model in which parameter estimates were free to differ across genders did not fit better than the model in which parameter estimates were constrained across genders (Δχ2(10) = 8.72, p = 0.56). Exploratory analyses examining the association between the individual forms of maltreatment (i.e., physical maltreatment and neglect) and conduct problems also indicated similar results: moderate to large portions of the covariance due to common genetic factors, small to moderate portions to common shared- and twin-environmental factors, and at most small portions to common nonshared environmental factors.
