ABSTRACT. Objectives. Physical aggression in children is a major public health problem. Not only is childhood physical aggression a precursor of the physical and mental health problems that will be visited on victims, but also aggressive children themselves are at higher risk of alcohol and drug abuse, accidents, violent crimes, depression, suicide attempts, spouse abuse, and neglectful and abusive parenting. Furthermore, violence commonly results in serious injuries to the perpetrators themselves. Although it is unusual for young children to harm seriously the targets of their physical aggression, studies of physical aggression during infancy indicate that by 17 months of age, the large majority of children are physically aggressive toward siblings, peers, and adults. This study aimed, first, to identify the trajectories of physical aggression during early childhood and, second, to identify antecedents of high levels of physical aggression early in life. Such antecedents could help to understand better the developmental origins of violence later in life and to identify targets for preventive interventions.Methods. A random population sample of 572 families with a 5-month-old newborn was recruited. Assessments of physical aggression frequency were obtained from mothers at 17, 30, and 42 months after birth. Using a semiparametric, mixture model, distinct clusters of physical aggression trajectories were identified. Multivariate logit regression analysis was then used to identify which family and child characteristics, before 5 months of age, predict individuals on a high-level physical aggression trajectory from 17 to 42 months after birth.Results. Three trajectories of physical aggression were identified. The first was composed of children who displayed little or no physical aggression. These individuals were estimated to account for ϳ28% of the sample. The largest group, estimated at ϳ58% of the sample, followed a rising trajectory of modest aggression. Finally, a group, estimated to comprise ϳ14% of the sample, followed a rising trajectory of high physical aggression. Best predictors before or at birth of the high physical aggression trajectory group, controlling for the levels of the other risk factors, were having young siblings (odds ratio [OR]: 4.00; confidence interval [CI]: 2.2-7.4), mothers with high levels of antisocial behavior before the end of high school (OR: 3.1; CI: 1.1-8.6), mothers who started having children early (OR: 3.1; CI: 1.4 -6.8), families with low income (OR: 2.6; CI: 1.3-5.2), and mothers who smoked during pregnancy (OR: 2.2; CI: 1.1-4.1). Best predictors at 5 months of age were mothers' coercive parenting behavior (OR: 2.3; CI: 1.1-4.7) and family dysfunction (OR: 2.2; CI: 1.2-4.1). The OR for a high-aggression trajectory was 10.9 for children whose mother reported both high levels of antisocial behavior and early childbearing.Conclusions. Most children have initiated the use of physical aggression during infancy, and most will learn to use alternatives in the following years before...

Background

A discussion of gender and conduct disorder must first answer the basic questions of whether or not there are any differences in prevalence, symptoms, and correlates of conduct disorder by sex. Several epidemiologic studies have found no difference in the prevalence of conduct disorder in adolescence by sex. Correlates of conduct disorder in girls are similar to those in boys (including aggression and internalizing disorders), once base rates of the correlates are accounted for. A major problem in studying conduct disorder in girls is the lack of appropriate criteria; theDiagnostic and Statistical Manual(3rd ed., rev.) criteria are not appropriate for girls. A case is made for sex-specific criteria for conduct disorder that take into account known differences in male and female childhood cultures and base-rate differences in aggression and criminality. Until basic issues of diagnosis and prevalence are resolved, other issues such as risk factors and developmental pathways cannot be successfully addressed.

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