title: Physical aggression during early childhood: trajectories and predictors.
abstract: BACKGROUND
  This study aimed to identify the trajectories of physical aggression during early childhood and antecedents of high levels of physical aggression early in life.
  
  
  METHODS
  572 families with a 5-month-old newborn were recruited. Assessments of physical aggression frequency were obtained from mothers at 17, 30, and 42 months after birth. Using a semiparametric mixture model and multivariate logit regression analyses, distinct clusters of physical aggression trajectories were identified, as well as family and child characteristics that predict high level aggression trajectories.
  
  
  RESULTS
  THREE TRAJECTORIES OF PHYSICAL AGGRESSION WERE IDENTIFIED: 1. children (28% of sample) who displayed little or no physical aggression, 2. approximately 58% followed a rising trajectory of modest aggression, and 3. a rising trajectory of high physical aggression (14%).
  
  
  CONCLUSIONS
  Children who are at highest risk of not learning to regulate physical aggression in early childhood have mothers with a history of antisocial behaviour during their school years, mothers who start childbearing early and who smoke during pregnancy, and parents who have low income and have serious problems living together. Preventive interventions should target families with high-risk profiles on these variables.
authors.affiliation: University of Montreal, Montreal, Quebec.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Tremblay
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Nagin
authors.forename: Jean R
authors.initials: JR
authors.lastname: Séguin
authors.forename: Mark
authors.initials: M
authors.lastname: Zoccolillo
authors.forename: Philip D
authors.initials: PD
authors.lastname: Zelazo
authors.forename: Michel
authors.initials: M
authors.lastname: Boivin
authors.forename: Daniel
authors.initials: D
authors.lastname: Pérusse
authors.forename: Christa
authors.initials: C
authors.lastname: Japel