Almost half of all homeless men who took part in a study by St. Michael's Hospital had suffered at least one traumatic brain injury in their life and 87 per cent of those injuries occurred before the men lost their homes.

While assaults were a major cause of those traumatic brain injuries, or TBIs, (60 per cent) many were caused by potentially non-violent mechanisms such as sports and recreation (44 per cent) and motor vehicle collisions and falls (42 per cent).

The study, led by Dr. Jane Topolovec-Vranic, a clinical researcher in the hospital's Neuroscience Research Program, was published today in the journal CMAJ Open.

Dr. Topolovec-Vranic said it's important for health care providers and others who work with homeless people to be aware of any history of TBI because of the links between such injuries and mental health issues, substance abuse, seizures and general poorer physical health.

The fact that so many homeless men suffered a TBI before losing their home suggests such injuries could be a risk factor for becoming homeless, she said. That makes it even more important to monitor young people who suffer TBIs such as concussions for health and behavioural changes, she said.

Dr. Topolovec-Vranic looked at data on 111 homeless men aged 27 to 81 years old who were recruited from a downtown Toronto men's shelter. She found that 45 per cent of these men had experienced a traumatic brain injury, and of these, 70 per cent were injured during childhood or teenage years and 87 per cent experienced an injury before becoming homeless.

In men under age 40, falls from drug/alcohol blackouts were the most common cause of traumatic brain injury while assault was the most common in men over 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, said Dr. Topolovec-Vranic.

This study received funding from the Canadian Institutes of Health Research and the Ontario Neurotrauma Foundation.

Separately, a recent study by Dr. Stephen Hwang of the hospital's Centre for Research on Inner City Health, found the number of people who are homeless or vulnerably housed and who have also suffered a TBI may be as high as 61 per cent -- seven times higher than the general population.

Dr. Hwang's study, published in the Journal of Head Trauma Rehabilitation, is one of the largest studies to date investigating TBI in homeless populations. The findings come from the Health and Housing in Transition Study, which tracks the health and housing status of homeless and vulnerably housed people in Toronto, Vancouver and Ottawa.