Head injuries can dramatically increase the chances of someone committing a violent crime, European researchers say. British and Swedish scientists carried out the research on a group of 22,914 traumatic brain injury victims and found almost 9 percent went on to commit acts of violence after diagnosis, three times the rate in the general population. The scientists conducting the study defined violent criminals as those convicted of homicide, assault, robbery, arson, sexual offences, or illegal threats or intimidation, Britain\'s The Independent newspaper reported. Epilepsy was also investigated in the study, as previous research had suggested it can increase the risk of violence, but the researchers said they found no significant association between epilepsy and violent crime.