Half of 16- to -18-year boys and girls entering New York City jails, according to a new study, say they’ve had a traumatic brain injury before being incarcerated. The prior injury(ies) resulted in either loss of consciousness, amnesia or both, reports the AP, and most were caused by assaults. Concussion studies among retired NFL players gained note some years ago but a growing body of research now focuses on the prevalence of prior traumatic brain injury among youth offenders. The rate of TBI in the unincarcerated youth population is 15 to 30 percent.

Researchers postulate that prior TBI–just one or multiple, it’s unclear–explains violent behavior, poor impulse control and decision-making, and high rates of recidivism. Reports don’t indicate whether the New York City sample of 300 boys and 84 girls separated violent from non-violent offenders. Most 16-to-18-year-olds in New York City jails (75 percent) are in for violent crimes, including robbery, homicide, weapons possession and assault. 

Results come from a medical questionnaire distributed to incoming offenders.

(h/t AP)