Immediate and sustained effects of parenting on physical aggression in Canadian children aged 6 years and younger

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. Key Words: parenting, child rearing, child behaviour, behaviour mechanisms, aggression, epidemiology, longitudinal studies Aggressive behaviour in young children (aged 6 years or younger) is a serious mental health issue with rates between 7% and 26% in epidemiologic samples from several countries. ' Physical aggression is one form of externalizing problems characterized by threats or physical attacks on other children and adults and includes bullying or initiating physical fights that can cause harm to others.2 While most children learn to regulate aggression at a young age,3'4 17% of Canadian children in a representative sample followed a highly stable developmental trajectory of aggression.3,5 Young children who exhibit physical aggression are at increased risk for future juvenile delinquency,6'7 school grade retention,8 adult criminality, and psychiatric disorders.1 Many children experience comorbidities that place them at even greater risk for persistent externalizing problems9 for which there are few effective interventions.10 Numerous cross-sectional and longitudinal studies have identified multiple combinations of factors associated with aggression in young children. Child Factors Boys exhibit higher absolute levels of aggression than girls11,12 and these differences tend to remain stable throughout childhood. …