The Connection Between Mental Illness and Homelessness

Updated September 2026

About 67% of people experiencing homelessness currently live with a mental health disorder, and 77% have at some point in their lives, according to a 2024 JAMA Psychiatry review of 85 studies covering 48,414 people. Serious mental illnesses are far less common - schizophrenia affects 7% and bipolar disorder 8%.

Ask ten people what share of the homeless population is mentally ill, and you'll get ten answers. Most are wrong in the same direction, and most are wrong because the question is quietly doing two different jobs at once.

"Mental illness" can mean a diagnosable condition of any kind - depression, anxiety, a substance use disorder. Or it can mean serious mental illness: schizophrenia, bipolar disorder, the conditions people picture when they imagine someone talking to themselves on a sidewalk. The honest answers to those two questions sit more than fifty percentage points apart.

That gap isn't a technicality. It shapes how a community funds shelter beds, how a police department writes its crisis-response policy, and whether the person sleeping in a doorway gets offered a case manager or a citation. Here's what the research actually says, what the picture looks like in Erie County, and where to find help in Pennsylvania.

How many people experiencing homelessness have a mental illness?

The most rigorous answer available comes from a 2024 systematic review and meta-analysis published in JAMA Psychiatry. Researchers at the University of Calgary pooled 85 studies covering 48,414 people experiencing homelessness, drawn mostly from the United States, Canada, and Germany.

Source: Barry R, Anderson J, Tran L, et al. Prevalence of Mental Health Disorders Among Individuals Experiencing Homelessness: A Systematic Review and Meta-Analysis. JAMA Psychiatry. 2024;81(7):691–699.

For comparison, roughly 13–15% of the general population has a current mental health disorder. The rates also split sharply by gender: 86% of men experiencing homelessness have had a mental health disorder at some point in their lives, compared with 69% of women.

Serious mental illness is a much smaller number

This is where most coverage of the subject goes wrong, and it's worth slowing down on.

The 67% figure covers every diagnosable condition in the book - a substance use disorder counts, a depressive episode counts. It is not a count of people living with schizophrenia or bipolar disorder.

Look at the same study's individual numbers and the picture changes shape. Schizophrenia sits at 7%. Bipolar disorder sits at 8%. Broader US estimates of serious mental illness among people experiencing homelessness generally land between 20% and 30% - still several times the general-population rate, and still nowhere near two-thirds.

Researchers reviewing the study made the point plainly: collapsing substance use disorder, personality disorder, schizophrenia, and depression into one percentage tells you almost nothing about any person.

The distinction matters operationally, not just editorially. Someone managing a depressive episode after losing an apartment needs something different from someone with untreated schizophrenia who has been unsheltered for three years. Both need mental health screening and assessment before anyone can say which supports will actually help.

Does homelessness cause mental illness, or the other way around?

Both, and the research is careful not to claim more than that.

The JAMA authors describe the relationship as bidirectional: a mental health disorder can raise a person's risk of losing housing, and losing housing can trigger or worsen a previously manageable condition. Their study measured how common these conditions are. It did not establish which came first.

Other factors push in both directions at once. Traumatic brain injury is among the clearest. A 2020 Lancet Public Health meta-analysis found that 53% of homeless and marginally housed people had sustained a TBI at some point in their lives, and 23% a moderate or severe one - roughly ten times the general-population rate for the severe category. A brain injury is both a plausible route into homelessness and a common consequence of it.

The practical takeaway: "treat the illness" and "provide housing" are not competing strategies. Housing stabilization services and behavioral health support tend to fail separately and work together.

What this looks like in Erie County

Every January, communities receiving HUD funding conduct a Point-in-Time (PIT) count - a one-night snapshot of how many people are experiencing homelessness locally. The Erie County Home Team, a coalition of community organizations that includes ECCM, coordinates the local count.

The count taken on the night of January 25, 2024 found:

• 454 Erie County residents experiencing homelessness
• 76 of them unsheltered, in places not meant for human habitation
• 378 in emergency shelter or transitional housing
• 37 families, accounting for 116 people, including 73 children under 18
• 47% of the adults counted living with a mental illness, and 36% with a substance use disorder
• An additional 577 people residing in permanent supportive or rapid rehousing programs

A one-night count undercounts, by design. It misses people doubled up on a relative's couch, people sleeping in cars parked out of sight, and anyone who avoided contact that night. Treat 454 as a floor, not a total.

Why people become homeless

Mental illness is one thread in a knot. The most common contributing factors:

• Not enough affordable housing. The most consistent predictor across US cities.
• Loss of income - a job ending, hours cut, or public assistance running out.
• Housing discrimination based on race, ethnicity, immigration status, or sexual orientation.
• Medical costs that can't be paid.
• A traumatic event - a house fire, a serious injury, the death of a household's primary earner.
• Fleeing domestic violence.
• Mental health and substance use challenges, which can contribute to losing housing and get harder to manage once it's gone.
• Justice system involvement. Time in jail disrupts housing, employment, and treatment simultaneously - a pattern we look at more closely in our post on mental illness and incarceration.

No single factor explains homelessness, which is why no single intervention ends it.

How ECCM helps

ECCM is a care coordination agency, not a direct service provider. We don't run the shelters, and we don't provide the therapy. What we do is connect people to the treatment, benefits, and housing supports that already exist, then stay with them to make sure the pieces hold together. For someone managing a mental illness without stable housing, that coordination is usually the part that breaks first.

Several of our programs work directly with people experiencing homelessness in Northwestern Pennsylvania:

• Homeless Persons Behavioral Health supports adults with serious mental illness who are in emergency shelters, in places not fit for habitation, doubled up, or facing eviction. Case managers link them to treatment, rehabilitation, and housing resources.
• Shelter Plus Care is a HUD-funded program providing permanent supportive housing and rental assistance to people who have experienced chronic homelessness and have a qualifying disability, paired with participation in treatment.
• Coordinated Entry is the front door - the process that assesses someone's situation and routes them to the right housing resource in the community.
• Representative payee services help people manage benefit income so rent gets paid first, which is often what keeps housing from slipping away a second time.
• Forensic case management works with individuals whose mental illness has brought them into contact with the justice system, where housing instability is usually part of the same story.

We've written more about how shelter programs and behavioral health services reinforce each other, and about the mental health case management process if you want to know what working with a case manager actually involves.

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