(PhysOrg.com) -- Young people who have sustained a head injury during their lifetime are more likely to engage in violent behavior, according to an eight-year study from the University of Michigan School of Public Health.
Further, the research found that young people who suffered a recent head injury (within a year of being questioned for the study) were even more likely to report violent behavior.
The report, which appears in the current issue of the journal Pediatrics, is one of the few studies to examine long-term effects of head injuries in a general population of young adults. Most other similar studies were conducted in prison populations.
There's been a recent blitz of media and research attention regarding youth, college and professional athletes who suffer head injuries and concussions while playing. This study is broader, but confirms previous findings about the connection between violence and head injuries, says lead author Sarah Stoddard, a research assistant professor at the School of Public Health.
"These are not necessarily sports-playing injuries," said Stoddard, who also is a research fellow at the U-M School of Nursing. "They could be from a car accident or from previous violent behavior, but it does support some of the sports research that's been going on with concussions."
Stoddard used data from the School of Public Health's Flint Adolescent Study, which looks at many issues regarding urban youth. Marc Zimmerman, professor of public health and chair of the U-M Department of Health Behavior and Health Education, is the principal investigator on that study.
The researchers followed a group of ninth-graders from four schools in Flint, Mich., into young adulthood. They conducted annual interviews over eight years. In years five and six, participants were asked if they had ever sustained a head injury. Those who said yesabout 23 percentreported more violent behavior in year eight of the study.
Moreover, Stoddard and Zimmerman examined the proximal relationship between a head injury and violent behavior and found that an injury reported in year seven of the study predicted violent behavior in year eight.
"We found that the link between a head injury and later violence was stronger when a head injury was more recent, even after controlling for other factors including previous violent behavior," Stoddard said.
The results also suggest that adolescents and young adults who have suffered a head injury that did not interfere with their ability to participate in an hour-long interview may still experience significant adverse developmental or behavioral effects.
The researchers defined a head injury as having been knocked unconscious or sustaining a concussion or a fractured skull.
Traumatic brain injury is a serious public health issue, they say. An estimated 1.7 million people annually sustain a TBI, and that only includes people who get medical care, so the number is likely much higher. Roughly 75 percent of head injuries are mild and many do not receive medical attention, but any TBI disrupts the function of the brain. Long-term impact can include changes in cognition, language and emotion, including irritability, impulsiveness and violence.