Ask where the largest concentrations of people with serious mental illness live in America, and the honest answer is not a hospital or a clinic. It is a jail. Over the past half-century, as state psychiatric hospitals closed and community mental health systems failed to absorb the people they once served, the criminal justice system became the default institution of last resort. The result is measurable in the government’s own numbers: mental illness is not an occasional feature of the incarcerated population — it is the majority experience.
The most authoritative data come from the Bureau of Justice Statistics (BJS), which has surveyed prisoners and jail inmates directly about their mental health. Those surveys tell a consistent story. A history of mental health problems is common behind bars, current psychological distress runs several times higher than in the general public, and only a fraction of the people who meet the clinical threshold for serious distress are receiving any treatment while incarcerated. This article walks through those figures, keeping careful track of a distinction that is easy to blur but essential to get right: prison data and jail data come from different surveys, collected years apart.
If you or someone you know is struggling or in crisis, help is available. Call or text 988 to reach the 988 Suicide & Crisis Lifeline, available 24/7.
A Note on the Data: Two Surveys, Not One
Before the numbers, a word on sourcing — because most reporting on this topic quietly mixes two separate studies.
Prison figures in this article come from the BJS 2016 Survey of Prison Inmates, which covers state and federal prisons only. Jail figures come from an older BJS report, Indicators of Mental Health Problems Reported by Prisoners and Jail Inmates, 2011–12. That 2011–12 collection remains the newest BJS source that covers jails, and it is now roughly thirteen years old — a genuine limitation worth naming plainly. Prisons hold people serving longer sentences after conviction; jails hold people awaiting trial or serving short terms, with far more churn. Because the two settings and the two survey years differ, the figures are not interchangeable, and we label each throughout.
Mental Illness in State and Federal Prisons
In the 2016 survey, 43% of state prisoners and 23% of federal prisoners reported a history of a mental health problem (BJS, 2016). A history is a broad measure — it captures anyone ever told by a professional that they had a mental disorder — but the gap between the two systems is itself informative, reflecting differences in who ends up in state versus federal custody.
BJS also measured current distress using a validated screening scale for serious psychological distress (SPD) in the past 30 days. By that stricter standard, 14% of state prisoners and 8% of federal prisoners met the threshold for serious psychological distress (BJS, 2016). SPD is a clinically meaningful marker: in the general population it strongly predicts a diagnosable, impairing mental illness.
| Indicator (BJS 2016 Survey of Prison Inmates) | State prisoners | Federal prisoners |
|---|---|---|
| History of a mental health problem | 43% | 23% |
| Serious psychological distress (past 30 days) | 14% | 8% |
| Told they had major depressive disorder | 27% | 14% |
The single most commonly reported disorder was major depression. 27% of state prisoners and 14% of federal prisoners said they had been told they had major depressive disorder — more than any other specific condition BJS asked about (BJS, 2016). Depression’s prominence behind bars is a reminder that the overlap between incarceration and mental illness is not confined to the disorders most associated with public stereotypes; it runs straight through the most common condition in the general population as well.
Women in Prison Carry a Heavier Burden
The distress figures widen sharply when broken out by sex. Women in prison reported serious psychological distress at higher rates than men in both systems: among state prisoners, 19% of women versus 14% of men; among federal prisoners, 17% of women versus 7% of men (BJS, 2016).
| Serious psychological distress, past 30 days (BJS 2016) | Women | Men |
|---|---|---|
| State prisoners | 19% | 14% |
| Federal prisoners | 17% | 7% |
This tracks a broader pattern seen outside prison walls, where women are diagnosed with mood and anxiety disorders more often than men — a divergence we examine in our analysis of mental health statistics by gender. Inside a correctional setting, where trauma histories are common and psychiatric care is thin, that elevated baseline distress becomes even harder to address.
Mental Illness in Jails
Jails are where the mental health crisis of the justice system is most acute — and, thanks to the aging of the data, least well measured. According to the BJS 2011–12 report, 44% of jail inmates had a history of a mental health problem, compared with 37% of prisoners in the same collection (BJS, 2011–12). Jails, in other words, held a higher share of people with a mental health history than prisons did.
The gap grows starker on current distress. 26% of jail inmates — roughly one in four — met the threshold for serious psychological distress, versus 14% (about one in seven) of prisoners (BJS, 2011–12). That jail figure is the number that most directly captures the phenomenon researchers describe as the criminalization of mental illness: people in acute distress cycling through booking and holding rather than through clinical care.
| Indicator (BJS 2011–12, jails and prisons) | Prisoners | Jail inmates |
|---|---|---|
| History of a mental health problem | 37% | 44% |
| Serious psychological distress | 14% (about 1 in 7) | 26% (about 1 in 4) |
Why are jail rates so much higher? Jails sit at the front door of the system. They absorb people arrested during a psychiatric emergency, people picked up on low-level charges tied to untreated illness, and people who have not yet been sorted toward treatment, release, or a prison sentence. The population is transient and, at the moment of intake, often in crisis.
The Treatment Gap Behind Bars
The most sobering figure in the 2011–12 report is about care, not diagnosis. Among incarcerated people who met the threshold for serious psychological distress, only about one-third were receiving mental health treatment at the time of the survey (BJS, 2011–12). Two out of three people in acute, screenable distress were going without.
That shortfall is a version of a problem that exists across the whole country — most people with mental illness in America receive no treatment — but it is concentrated and intensified inside facilities that were never designed to be clinics. Our overview of the mental health treatment gap traces the same barriers of cost, workforce shortages, and access that leave so many untreated on the outside; incarceration removes a person’s ability to seek care on their own terms and hands responsibility to institutions that are chronically under-resourced for it.
How This Compares to the General Population
The scale of these numbers only lands when set against the baseline. In the general adult population, serious mental illness affected 5.6% of U.S. adults in 2024 (SAMHSA, 2024). Serious psychological distress and serious mental illness are not identical measures, but they occupy the same clinical territory — impairing conditions that warrant treatment.
Against that 5.6% baseline, the incarcerated figures are several times higher: 14% of state prisoners, 19% of women in state prison, and 26% of jail inmates met the distress threshold in their respective surveys. People who are justice-involved are, by the government’s own measures, among the populations most affected by mental illness in the country — a status they share with people experiencing homelessness, a group with heavy overlap given how often untreated illness, housing instability, and arrest travel together.
The Criminalization of Untreated Illness
Put the pieces together and a pattern emerges. A large share of incarcerated people arrive with a documented history of mental illness. A smaller but still striking share are in acute distress at the time of the survey — far above the rate in the free population. Most of those in distress are not being treated. And the concentration is heaviest in jails, the part of the system closest to the initial police encounter.
This is what advocates and researchers mean when they describe jails as de facto psychiatric facilities. It is not a claim that mental illness causes crime; it is an observation that when treatment systems fail, the justice system inherits the people they leave behind. Substance use disorders compound the picture — they co-occur frequently with serious mental illness, and untreated substance use disorder is itself a common pathway into custody. Diversion programs, mental health courts, and in-custody treatment exist to interrupt that cycle, but the BJS data make plain how much unmet need remains inside the walls.
Frequently Asked Questions
What percentage of prisoners have a mental illness?
In the BJS 2016 Survey of Prison Inmates, 43% of state prisoners and 23% of federal prisoners reported a history of a mental health problem. By the stricter measure of serious psychological distress in the past 30 days, 14% of state prisoners and 8% of federal prisoners met the threshold (BJS, 2016).
Do jails or prisons have higher rates of mental illness?
Jails do. In the BJS 2011–12 data, 44% of jail inmates had a history of a mental health problem versus 37% of prisoners, and 26% of jail inmates met the threshold for serious psychological distress versus 14% of prisoners. Jails sit at the front of the system and absorb many people in acute crisis.
How does mental illness in prison compare to the general public?
It is several times more common. Serious mental illness affected 5.6% of U.S. adults in 2024 (SAMHSA, 2024), while 14% to 26% of incarcerated people met the threshold for serious psychological distress in the BJS surveys, depending on the setting and the year measured.
Do incarcerated people with mental illness get treatment?
Often not. In the BJS 2011–12 report, only about one-third of incarcerated people who met the threshold for serious psychological distress were receiving mental health treatment at the time of the survey — meaning roughly two-thirds were not.
Why are the prison and jail numbers from different years?
The BJS 2016 Survey of Prison Inmates covers prisons only. The most recent BJS study that includes jails is the 2011–12 report, now about thirteen years old. Because the surveys differ in setting and year, prison and jail figures should not be treated as interchangeable, which is why we label each throughout.
Sources
-
Maruschak LM, Bronson J, Alper M. Indicators of Mental Health Problems Reported by Prisoners: Survey of Prison Inmates, 2016. Bureau of Justice Statistics; 2021. https://bjs.ojp.gov/library/publications/indicators-mental-health-problems-reported-prisoners-survey-prison-inmates
-
Bronson J, Berzofsky M. Indicators of Mental Health Problems Reported by Prisoners and Jail Inmates, 2011–12. Bureau of Justice Statistics; 2017. https://bjs.ojp.gov/content/pub/pdf/imhprpji1112.pdf
-
Substance Abuse and Mental Health Services Administration. 2024 National Survey on Drug Use and Health (press release). SAMHSA; 2025. https://www.samhsa.gov/newsroom/press-announcements/20250728/samhsa-releases-annual-national-survey-on-drug-use-and-health