Most studies of childhood behavioral disinhibition have focused on conduct disturbances. We chose to include hyperactivity firstly because hyperactivity and conduct disturbances both predict later-onset externalizing behaviors, for example, these behaviors in boys aged eight predict frequent drunkenness 10 years later (Niemela et al, 2006). Secondly, these behaviors may follow divergent paths; hyperactivity at age 6-7 years is a stronger predictor than conduct disturbances of poor social adjustment and relationship problems 10 year later (Danckaerts et al, 2000). In fact we did not detect G × E interaction effects on conduct disturbances, perhaps because this is a relatively weak phenotype in a general population sample of pre-pubertal children. Very few children had high conduct problem scores which may account for the negative G × E findings.
