Longitudinal data from juvenile offenders reveal troubling link between early life head injury, and impulsivity and aggression in later adolescence

Article authors Laugalis and Connolly investigated whether head injuries in childhood/early adolescence lead to the development in later adolescence of a range of antisocial personality traits that are strongly correlated with adult antisocial personality disorder. The authors used data from structured diagnostic interviews and assessments of the same group of juvenile offenders in the first two waves of the six-wave Northwestern Juvenile Project (NJP). A longitudinal study that began in 1995, the NJP followed a group of male and female youth detained at a juvenile temporary detention center in Cook County, Illinois. For their analysis, Laugalis and Connolly looked at 881 of the detainees for whom there was data captured in the 1995-1998 baseline interview about whether they had suffered a head injury during childhood/early adolescence. Strikingly, 45 percent of them reported experiencing at least one head injury, often from being hit with an object, being beaten up, or falling down. The researchers then analyzed data collected from the same respondents during the first follow-up interviews conducted in 1998-2001, when trained NJP interviewers assessed the youth for symptoms of antisocial personality disorder and related traits like impulsivity, aggression, and deceitfulness. Laugalis and Connolly conducted their analysis controlling for potentially confounding factors like ADHD, PTSD, abuse history, substance use, and intelligence. They found that youth who had suffered a head injury were 29 percent more likely to meet the criteria for the traits of impulsivity and failure to plan, and they were 35 percent more likely to exhibit the traits of irritability and aggression compared to those without a history of head injury. However, the authors did not find that head injuries were significantly tied to other antisocial personality traits like deceitfulness, reckless disregard for others, irresponsibility, or lack of remorse. Additionally, they found that the more head injuries a youth had experienced, the stronger the connection to aggressive behavior in late adolescence.