People who suffer a traumatic brain injury as a child are more likely to commit offenses as adults, researchers say.
Professor Randolph Grace of the University of Canterbury, and Dr Audrey McKinlay from Melbourne's Monash University, studied Canterbury children who had experienced a brain injury as a child from birth to 17 years old.
The participants were now 18 years or older and more than five years had passed since their injury.
A traumatic brain injury is caused by an external force, such as a bump or blow to the head, which disrupts the normal function of the brain. The effects range from mild memory difficulties to dementia, seizures and depression.
The researchers looked at participants' lifetime involvement in offending behaviour, and also assessed the participants on emotional behaviour, looking at malevolent aggression, social anxiety and social self-esteem.