Developmental pathways of physical aggression from infancy to early school age

This study identified latent trajectories of physical aggression from infancy to preschool age and tested for (a) early parent, parenting and child predictor effects on trajectory membership and (b) trajectory-effects net of parent, parenting, and child predictor effects on Grade 2 social, behavioral and academic functioning. We used data from the Behavior Outlook Norwegian Developmental Study (BONDS), comprising 1,159 children (559 girls). Parents reported on risk and protective factors, and on physical aggression from 1 to 5 years; teachers reported on Grade 2 outcomes. We employed latent class growth curve analyses to identify nine aggression trajectories. In fully adjusted models testing simultaneously all associations among predictors, trajectories, and outcomes, maternal and paternal harsh parenting, child gender, and sibling presence predicted trajectory membership, which significantly predicted Grade 2 externalizing. Child gender had a pervasive influence on all outcomes as well as on trajectory membership. This is the first trajectory study that attempts to sort out which predictors are most proximal, more distal, or just confounded, with their relative direct effect sizes, and to link early paternal as well as maternal harsh parenting with childrens development of physical aggression from infancy to preschool age. Our findings underscore the need to include fathers in developmental research and early prevention and intervention efforts.