Objective: To determine whether the effects of factors associated with the development of childhood (aged 6 years or younger) physical aggression were immediate (cross-sectional), sustained (longitudinal), or both.
Methods:A longitudinal subsample (n = 975) of children born between December 1994 and April 1995 was drawn from the Canadian National Longitudinal Survey of Children and Youth and followed from birth to 6 years of age. Using random-and fixed-effects logistic panel regression models, child (sex and preterm birth), maternal (education, employment, and positive or hostile/ineffective parenting), and family (lone-parent, older and younger siblings, and income) indicators were regressed on childhood physical aggression.Results: Hostile/ineffective parenting contributed significantly to explaining the variance in aggression. At each measurement time point (birth, 2, 4, and 6 years of age), a change in hostile/ineffective parenting had an effect on aggression, and this effect carried forward across time up to 6 years. Being a boy, having a mother with less education, and living in a lone-parent family with siblings also contributed significantly to aggression. Preterm birth, maternal employment, depressive symptoms, positive interaction, and income failed to contribute significantly to aggression.
Conclusions:These results support the hypothesis that hostile/ineffective parenting has an immediate effect on aggression. Contrary to predictions that it would have an immediate effect only at the time it was occurring, hostile/ineffective parenting had a sustained effect on aggression that carried forward in time up to 6 years of age. The results suggest that hostile/ineffective parenting has an effect on aggression prior to any evidence of aggressive behaviour in the child.Can J Psychiatry. 2008;54(1):55-64.Clinical Implications · Parenting interventions need to begin early in a child's development and continue at least until school age to have the greatest impact on the prevention of aggression. · Boys who live in lone-parent families with multiple siblings and mothers with low education may benefit the most from interventions to prevent aggression. · Repeated screening for physical aggression in young children may be useful to predict those who will continue on a trajectory of physical violence into adolescence.Limitations · Single informant (mother) reporting is not equivalent to direct observation of the child. · Random-and fixed-effects models do not explain the mechanisms leading to aggression. · Standardizing scores adjusts for qualitative differences in measures of development, but is not a perfect solution.