Most Homeless People Have Mental Health Disorders

Most people experiencing homelessness have mental health disorders, according to a systematic review and meta-analysis.

In an examination of studies that included nearly 50,000 participants, the current prevalence of mental health disorders among people experiencing homelessness was 67% and the lifetime prevalence was 77%.

Rebecca Barry

"The relationship is likely bidirectional, where experiencing homelessness may exacerbate mental health symptoms or where having a mental health disorder may increase an individual's risk for experiencing homelessness," lead author Rebecca Barry, PhD, a postdoctoral fellow at the University of Calgary in Calgary, Canada, told Medscape Medical News. 

"There are also likely stressors that increase both risk for homelessness and risk for developing mental health disorders. This study examines prevalence but does not examine causal relationships," she said.

The findings were published on April 17, 2024, in JAMA Psychiatry.

A Growing Problem 

To determine the current and lifetime prevalence of mental health disorders among the homeless population, the researchers analyzed 85 studies that examined this question in participants aged ≥ 18 years. The review included 48,414 participants, including 11,154 (23%) women and 37,260 (77%) men.

The lifetime prevalence of mental health disorders was significantly higher in men experiencing homelessness (86%) compared with women (69%). The most common mental health disorder was substance use disorder (44%), followed by antisocial personality disorder (26%), major depression (19%), bipolar disorder (8%), and schizophrenia (7%). 

The prevalence of current and lifetime mental health disorders among the homeless population was higher than those observed in the general population (13%-15% and 12%-47%, respectively). 

The results resembled those of a previous review that estimated that 76% of people experiencing homelessness living in high-income countries have mental health disorders.

Dallas Seitz, MD

"Even though our results are not surprising, they still are drawing attention to this issue, because it is a big problem in Canada, the United States, Europe, and other places," senior author Dallas Seitz, MD, PhD, professor of psychiatry at the University of Calgary's Cumming School of Medicine, told Medscape Medical News. "The problem is concerning, and it's not getting better. Addiction and mental health problems are becoming more common among people who are homeless." 

The bottom line is that people need affordable housing and mental health support, said Seitz. "It's a housing problem and a health problem, and we need adequate resources to find better ways for those two systems to collaborate. There are public safety concerns, and we have to try and bring services to people experiencing homelessness. You have to come and meet people where they're at. You have to try and establish a trusting relationship so that we can get people on the path to recovery." 

'It's Really About Income' 

Commenting on the findings for Medscape Medical News, Stephen Hwang, MD, professor of medicine at the University of Toronto, said, "There have been previous studies of this type, but it is good to have an updated one." Hwang, who is also chair in Homelessness, Housing, and Health at St. Michael's Hospital, did not participate in the research. 

The findings must be understood in the proper context, he added. For one thing, grouping together all mental health disorders and giving a single prevalence figure can be misleading. "They are including in that category a diverse group of conditions. Substance use disorder, personality disorder, schizophrenia, and depression are all lumped together. The 67% prevalence seems very high, but it is a combination of many different conditions. I just don't want people to look at that number and think that this means that everyone is a substance user or everyone has schizophrenia," said Hwang. 

Also, some readers might interpret the findings to mean that mental problems are the reason people are homeless, he added. "That would be an incorrect interpretation, because what this study is showing is that people with mental health disorders have a higher risk for becoming homeless. It doesn't mean that it caused their homelessness. What really causes homelessness is a lack of affordable housing," said Hwang.

"In a city or community where housing is very expensive, there's not enough for everyone to be housed, there is a lot of competition for housing, and there's not enough affordable housing for a number of reasons, we know that people with mental health conditions and substance use disorders will be among the first to lose their housing," he said.

"It's really about income. There are many reasons why a person cannot afford housing. So, not being able to earn enough money to afford it because you have a mental health disorder or substance use disorder is a common underlying reason for homelessness."

Hwang also pointed out that people with mental illness who can access support, either through family members or through mental health care, and who also have the income to afford such services do not become homeless.

"Schizophrenia is seen in every population of the world at a rate of 1%. But you travel to certain cities and you see people who appear to have schizophrenia wandering the streets, and you go to other cities in the world and you don't see anyone who looks like they're homeless and have schizophrenia," he said. 

"It's not because there are fewer people with schizophrenia in those cities or countries, it's because people with schizophrenia are treated differently. The rate of homelessness is determined not by how many people have that condition [eg, schizophrenia] but by how we treat those people and how we set up our society to either support or not support people who have disabilities." 

The study was funded by the Precision Care With Information, Science and Experience - Mental Health (PRECISE-MH) grant funded by the Calgary Health Foundation. Barry is supported by the Harley Hotchkiss Samuel Weiss Postdoctoral Fellowship awarded by the Hotchkiss Brain Institute at the University of Calgary. Barry reported having no relevant financial relationships. Seitz reported grants from Calgary Health Foundation during the conduct of the study as well as grants from University Health Foundation, the Canadian Institutes of Health Research, the Public Health Agency of Canada, the Alzheimer's Association, and the Hotchkiss Brain Institute. He received honoraria for guideline development from the Canadian Coalition for Seniors Mental Health outside the submitted work. Hwang reported no relevant financial relationships.