Many homeless men have suffered at least one traumatic brain injury in their life, according to a recent study.

Researchers from St. Michael's Hospital in Canada found that more than half of men living on the streets had at least one traumatic brain injury in their lifetime and 87 percent of those injuries occurred before the men lost their homes.

While assaults were a major cause of those traumatic brain injuries, 60 percent, many were caused by potentially non-violent mechanisms such as sports and recreation, 44 percent,   and motor vehicle collisions and falls, 42 percent researchers said.

"[It's] important for health care providers and others who work with homeless people to be aware of any history of [traumatic brain injury] because of the links between such injuries and mental health issues, substance abuse, seizures and general poorer physical health," researchers said in a statement.

Dr. Jane Topolovec-Vranic, a clinical researcher at St. Michael's Hospital's Neuroscience Research Program, said the fact that so many homeless men suffered a traumatic brain injury before losing their home suggests such injuries could be a risk factor for becoming homeless. She added that it makes it even more important to monitor young people who suffer brain injuries such as concussions for health and behavioral changes.

For the study, researchers looked at data on 111 homeless men aged 27 to 81 years old who were recruited from a downtown Toronto men's shelter.

They found that 45 percent of these men had experienced a traumatic brain injury, and of these, 70 percent were injured during childhood or teenage years and 87 percent experienced an injury before becoming homeless. In men younger than 40, falls from drug/alcohol blackouts were the most common cause of traumatic brain injury while assault was the most common in men older than 40 years old.

Recognition that a TBI sustained in childhood or early teenage years could predispose someone to homelessness may challenge some assumptions that homelessness is a conscious choice made by these individuals, or just the result of their addictions or mental illness, Dr. Topolovec-Vranic said.

The findings were recently published in the journal CMAJ Open.