According to SAMSHA:
Epidemiological estimates indicate that about one-third of all homeless, single adults have severe and persistent mental illness and have marked neuropsychological impairments in attention, executive functioning, verbal memory, and general intellectual functioning. Substance use and abuse estimates are extremely high for homeless adolescents and adults, including alcohol and injection drug use (ranging from 20-80%). Available data suggest that in major urban areas, 10-20% of homeless persons who suffer from chronic mental illnesses are infected with HIV.AIDS Housing of Washington explains why:
People with serious mental illnesses may be at increased risk for HIV infection. Reasons include higher rates of drug and alcohol use associated with high risk behaviors, a lack of safer sex education designed for people with major mental illnesses, and the increased vulnerability of people with mental illnesses to sexual assault and abuse, including in institutional settings. A study released in 2001 found that nearly half of people receiving care for HIV had a psychiatric disorder. Studies have also shown that depression is two to three times more common in people receiving HIV care than in the general population, affecting 22% to 32% of the total.BOR points out that the National Coalition for the Homeless ranks Houston and Dallas among the top 10 meanest cities in the country if you're homeless. (Go read it.) Sounds like some city fathers (and mothers) are also missing the link. Dallas bulldozes homeless "housing" when it's too visible; Houston has a thing about BO (the smelly kind, not BOR) and bans sitting on the sidewalk. Meh.