Health care for the homeless: what we have learned in the past 30 years and what's next.

In the 1980s, the combined effects of deinstitutionalization from state mental hospitals and the economic recession increased the number and transformed the demographic profile of people experiencing homelessness in the United States. Specialized health care for the homeless (HCH) services were developed when it became clear that the mainstream health care system could not sufficiently address their health needs. The HCH program has grown consistently during that period; currently, 208 HCH sites are operating, and the program has become embedded in the federal health care system. We reflect on lessons learned from the HCH model and its applicability to the changing landscape of US health care.