The U.S. has cut homelessness among veterans nearly in half since 2010, thanks largely to “housing first” programs. That flies in the face of the long-held assumption that most homeless veterans needed treatment for mental illness or substance abuse to prepare them to live in an apartment.

Arline Mathieu looked at the highly visible case of homelessness in 1980s New York City. She argues that, in those years, city officials exaggerated the links between homelessness and mental illness, leading to long-term public confusion.

In the early 1980s, political demonstrations, legal action, and reports drew public attention to homelessness in the city. Mayor Edward Koch, who was resisting pressure from New York State to open more shelters, argued that the state’s release of psychiatric patients was largely to blame for the problem. This was a convincing argument to many people because mentally ill people were the most visible of the homeless.

The media followed Koch’s lead in addressing homelessness as largely a question of mental health. At least three 1987 New York Times headlines used the general term “homeless” when the stories were specifically about psychiatric problems faced by a subset of people without homes. In 1986, after the Times wrote that “the proportion of those in shelters with serious psychiatric problems has been estimated at more than 70 percent,” a team of epidemiologists wrote in to call that estimate “grossly at odds with our recent research.” Their estimate was more like 25 percent in the city’s single-adult shelters, and that was without accounting for people living in family shelters or taking refuge with friends or family.

Many city policies focused on hiding homeless people from public sight. Police commonly removed people staying on the streets, in bus terminals, or on subways, and brought them to municipal hospitals, often without their consent, even if they were not diagnosed with mental illness.

Evidence showed that deinstitutionalization wasn’t a big driver of growing homelessness to begin with. For one thing, the release of patients from mental institutions occurred mostly in the 1960s and early ‘70s, but the rise in homelessness took place in the late ‘70s and into the 1980s. In 1986, the city found that 66 percent of its homeless people were families with children, not the stereotypical lone man with mental health problems. And in some cases living on the street or in a shelter was the cause, rather than the result, of episodes of mental illness.

Mathieu argues that the actual forces driving the growing homeless population were stagnating wages, cuts to public benefits like unemployment insurance and Social Security, and declining access to low-income housing.

This may help to explain why “housing first” policies have had so much success: in many cases, the root cause of homelessness was, simply, not being able to afford a home.