Another study found that a large number of homeless people have suffered a traumatic brain injury at some point in their lives:
"Researchers at St. Michael’s Hospital in Toronto surveyed 111 homeless men and found that 45 percent of them had suffered at least one traumatic brain injury (or TBI) in their life, and 87 percent of those injuries occurred before they were homeless. Among the general population, TBI rates are estimated to be 12 percent, according to a 2013 meta-analysis of studies from developed countries."
"Researchers at St. Michael’s Hospital in Toronto surveyed 111 homeless men and found that 45 percent of them had suffered at least one traumatic brain injury (or TBI) in their life, and 87 percent of those injuries occurred before they were homeless. Among the general population, TBI rates are estimated to be 12 percent, according to a 2013 meta-analysis of studies from developed countries."
http://m.huffpost.com/us/entry/5227637