Objectives This study aims to parse out the effects of childhood head injury (HI) as an acquired neuropsychological deficit that impacts adolescent delinquent behavior, while accounting for other early-life risk factors and potential temporal ordering. Methods Nationally representative prospective data from the UK Millennium Cohort Study (MCS; N = 13,287) and a series of logistic and binomial regressions are used to examine the relationship between early-life risk factors, HI, and adolescent delinquent behavior. Methodological considerations from clinical HI research, such as the use of an orthopedic injury comparison group, are incorporated. Results Findings are consistent with the conceptualization of HI as an acquired neuropsychological deficit, in that childhood HI increases the risk of early- and adolescent-onset delinquency, sustained delinquent behavior from childhood to early adolescence, and participation in a greater variety of delinquent behavior. Conclusions Childhood HI is relatively common, as over 27% of the sample reported at least one HI. The importance of HI as an acquired neuropsychological deficit and its relevance as a risk factor for later criminal behavior is reiterated. Future research should examine the importance of developmental period effects and mechanisms underlying this relationship.

Proximal changes in externalizing behaviors before and after children and earlyadolescents have their first alcoholic drinkand first heavydrinking episode are examined using intergenerational, prospective data from the ongoing U.K. national Millennium Co-hortStudy (10,529 child-parent pairs followedover35,406 occasions). Method: We examined howw ithin-personc hanges in externalizing behaviors (based on parental reports on the Strengths and Difficulties scale when children were modal ages5 ,7 ,1 1, and 14 years) follow children'sage at first alcoholic drink(AFD)and age at firstheavy drinking (AFHD), based on confidential child self-reports at ages 11 and 14 years. Analyses controlled for child age, time-varying parent-level confounders (parental education and alcohol abstention), and time-stable selection factors. Results: Estimates from fixed-effects Poisson models revealed a5%increase in the expected count of externalizing behaviors after children have their first alcoholic drink (incidence rate ratio [IRR] = 1.05, 95% CI [1.03, 1.07]), anda13% increase after first drinking heavily(IRR =1.13, 95% CI [1.09, 1.18]), independent of keytime-varying and alltime-stableindividual differences. Conclusions: Early AFHD and unobservedt ime-stable selection factors partiallye xplain relationships between earlydrinking and problem behaviors, butearlyAFD continues to be asignificant predictor of externalizingbehavior.Although prevention efforts should continue to discourage heavy drinking in childhood ande arlya dolescence, the results suggest that both AFHD and AFD should be delayed.