NFL players suffer repeated blows to the head as part of the game. And there is ample evidence to suggest that all those hits to the head increase the risk for neurodegenerative brain disorders, including dementia, Parkinson’s, and Lou Gehrig’s disease (ALS).
 

But do they also increase the propensity to commit domestic violence?
 

“It’s a very, very important question,” Adrian Raine, a psychologist at the University of Pennsylvania, told Forbes this week. “It’s a plausible hypothesis, without doubt.”
 

Raine, whose research has examined how brain function can help explain criminal behavior, said head injuries are not an excuse for the dozens of NFL players who have been arrested for domestic violence in the past few years.
 

“We have to be careful what we’re talking about from a causality standpoint,” Brian O’Connor of Futures Without Violence told Forbes. NFL players are trained to be aggressive and rewarded financially for it, which may also contribute to a “culture of violence” that can spill over from the field into players’ personal lives.
 

But new scientific research contact-sport athletes has shown there is little debate over whether football, and similar sports, damage the brains of players in ways that can have long-lasting consequences — including an increased risk for Alzheimer’s and personality changes that can include violent behaviors.
 

According to Forbes, domestic violence accounts for 48 percent of arrests for violent crimes among NFL players, compared to about 21 percent nationally. More than two-dozen pro football players, including Ray Rice, have been arrested for domestic abuse in the past five years alone.

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What’s more, research has found a neurobiological link in individuals who commit repeated acts of violence. In one recent, Raine scanned the brains of men arrested for domestic abuse and found neural abnormalities. The research also showed the men were much more likely to violently lash out when provoked by something as simple, such as a spouse’s nagging.
 

“We all get aggressive at times. What stops us from lashing out? It’s a well-functioning prefrontal cortex,” Raine told Forbes. “In spouse abusers, that guardian angel of behavior — that prefrontal cortex — is just not working as well.”
 

It’s possible that some of those problems are congenital, but it’s also possible that injuries to that region of the brain are a factor.
 

The NFL has increasingly acknowledged such potential links, noting in a new report out this month that almost 30 percent of NFL players suffer from at least moderate neurodegenerative brain disorder.
 

Football players appear to be especially at risk for a specific disease called chronic traumatic encephalopathy, or CTE, in which the brain deteriorates over time. Early CTE symptoms include “impulsivity, explosivity, and aggression,” said Ann McKee, M.D., a Boston University researcher, in a recent journal article.
 

The disease can only be detected with an autopsy, but has been found in the brains of high school and college football players, including football players who never had a diagnosed concussion.
 

BU neuroscientists have tested the brains of 62 former NFL players who suffered from symptoms like depression and violence — 59 of them tested positive for CTE. McKee has suggested a majority of professional football players could suffer from CTE.
 

“Is a concussion going to lead to CTE? No, probably not in most cases,” McKee told PBS Frontline last year. “But if you have enough concussions over a certain amount of time, yes, then I think you can lead to CTE.”

CTE has also turned up in the brains of football players linked with domestic violence. Junior Seau, aformer NFL star who was found to have CTE after his suicide in 2012, was arrested two years before his death on suspicion of assaulting his girlfriend.
 

In response to Ray Rice fallout, mental health experts are calling on the NFL to protect players’ partners and families, and actively screen and treat players for mental health problems.
 

“I do think we need to recognize that there’s more to domestic violence than … men’s using physical power to control women,” Raine contends in his book, “The Anatomy of Violence.” “We need to consider a contribution by the brain to spousal abuse.”