One in five homeless people suffers from untreated severe mental illness.

While about 6 percent of the general population suffers from severe mental illness, 20 to 25 percent of the homeless suffer from severe mental illness, according to government studies. Half of this population self-medicate and are at further risk for addiction and poor physical health. A University of Pennsylvania study tracking nearly 5,000 homeless people for two years discovered that investing in comprehensive health support and treatment of physical and mental illnesses is less costly than incarceration, shelter and hospital services for the untreated homeless.