Teacher-rated aggression and co-occurring problems and behaviors among schoolchildren: A comparison of four population-based European cohorts

Non-pathological levels of children9s co-occurring externalizing/internalizing problems in the school setting are not well characterized. We assessed associations between aggressive behavior and co-occurring externalizing/internalizing problems among schoolchildren in 39,936 teacher ratings from 4 population-based cohorts (FinnTwin12 from Finland, Generation R and the Netherlands Twin Register from the Netherlands, and the Twins Early Development Study from the UK). Correlations of aggressive behavior were high with other externalizing problems (0.47-0.80) and lower with internalizing problems (0.02-0.39). A negative association was seen with prosocial behavior, ranging -0.33 to -0.54. Although the mean levels of aggressive behavior differed significantly by gender, the correlations of aggressive behavior with co-occurring behaviors were notably more similar between the genders (e.g., aggressive-hyperactivity correlations: 0.51-0.75 boys, 0.47-0.70 girls). Comparisons are also discussed with respect to age, instrument/cohort, and parental ratings. These population-based European observations highlight the complexity of aggressive behavior at school, and can assist in creating appropriate interventions.