For those with CTE, family history of mental illness tied to aggression in middle age

CTE is a neurodegenerative disease associated with repeated head injuries, often seen in athletes and military personnel, that can lead to mood changes and dementia.

“This appears to be a case where together these risk factors add up to a greater risk for aggression than they each do on their own, where people with CTE and a family history of mental illness are much more likely to have aggressive behavior than those with just CTE or just the family history,” said study author Jesse Mez, MD, MS, of Boston University Chobanian & Avedisian School of Medicine and a member of the American Academy of Neurology.

The study involved 845 men who were exposed to repetitive head impacts through contact sports or military service. A total of 329 of them played professional football. All donated their brains to research after their death, which was at an average age of 60. Of the total group, 589, or 70%, had CTE and 383, or 45%, had a family history of mental illness.

Researchers interviewed family members or spouses of the participants about their aggressive behavior. They were also asked whether the participants’ parents, siblings or children were ever diagnosed with major depression, bipolar disorder, anxiety, post-traumatic stress disorder, obsessive-compulsive disorder or other mood or psychiatric disorders. If any family member had a diagnosis, the participant was considered to have a family history of mental illness.

Researchers then divided participants into four groups: 256 people, or 30%, with CTE and a family history of mental illness; 333 people, or 40%, with CTE and without a family history of mental illness; 127 people, or 15%, without CTE and with a family history of mental illness; and 129 people, or 15%, without CTE and without a family history of mental illness.

Researchers asked family members about the participants’ aggressive behavior, such as whether they had severe arguments with others or got in physical fights, where scores ranged from zero to 44. They found that during adulthood people with CTE and a family history of mental illness had an average score of 19 compared to people with CTE without a family history of mental illness who had an average score of 17.

“This relationship was most striking for participants who died between 40 and 59 years old,” Mez added.

After adjusting for other factors, such as total years playing contact sports and military history, researchers found that those who died between 40 and 59 years old who had CTE and a family history of mental illness scored an average of 0.64 standard deviations higher on a scale measuring aggression when compared to those with CTE, but without a family history of mental illness. For people who did not have CTE, having a family history of mental illness did not increase their risk for aggressive behavior.

“The link between a family history of mental illness and aggression may be through a shared genetic background and also through shared environment and common behaviors, such as childhood experiences with family members,” said Mez. “Identifying people who are more likely to show symptoms of aggression based on family history of mental illness would give us a way to predict the consequences of CTE and identify who may benefit most from treatment options.”

A limitation of the study was that the study relied on past information from family members and spouses who may not have remembered information accurately.

The study was funded by the National Institutes of Health, Department of Veterans Affairs and the Nick and Lynn Buoniconti Foundation.