New research suggests close to half of all homeless men who participated in a St. Michael's Hospital study had suffered a traumatic brain injury at some point in their lives.

Eighty-seven percent of these brain injuries (TBIs) had occurred before the study subjects had become homeless, a St. Michael's Hospital news release reported.

The majority of these brain injuries (60 percent) were caused by assaults others were a result of other activities such as sports or accidents in vehicles and other modes of transportation.

The researchers stressed that doctors working with homeless individuals should learn about their brain injury history because of possible side effects such as "health issues, substance abuse, seizures and general poorer physical health," the news release reported.

The fact that so many homeless people lost their homes after receiving a TBI suggests the two occurrences could be related; it also suggests young people who have received TBIs should be closely monitored.

To make their findings the researchers looked at 111 Toronto homeless men between the ages of 27 and 81. The team found 45 percent of them men had received a traumatic brain injury, 70 percent of which occurred during childhood or the teen years. 

In men under the age of 40 the most common cause of TBI was accidents that occurred while the individual was impaired by drugs or alcohol. Assault was the most common cause of TBI in men who sustained the injury over the age of 40.

"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," Doctor Jane Topolovec-Vranic, a clinical researcher in the hospital's Neuroscience Research Program said according to the news release.