Federal prisoners, including those with mental illness, are being kept in solitary confinement for long periods of time in violation of federal policy, according to a new report.

Although the Bureau of Prisons states that it does not practice solitary confinement, the Justice Department inspector general found inmates, including mentally ill prisoners, housed in single-cell confinement for extended periods and “with limited human contact,” the 96-page report said.

The Bureau of Prisons, part of the Justice Department, does not put a limit on the maximum amount of time that inmates can spend in what is known as “restrictive housing.” Inmates, including those with mental illness, may spend years and even decades in these types of cells.

At one prison, investigators found inmates who were confined to their cells for more than 22 hours a day and did not engage in recreation with each other or with other inmates.

“You have no contact, you don’t speak to anybody, and it’s a form of torture on some level,” a psychologist at one prison told the inspector general’s investigators.

In one case, a prisoner had been placed in single-cell confinement for about four years. In another case, a mentally ill inmate was placed in restrictive housing for 1,912 consecutive days, or five years. One mentally ill prisoner was there for six years. Investigators also found a mentally ill inmate who had spent 19 years in a maximum security facility until he was transferred to a residential mental health treatment program.

[Read the Justice Dept. inspector general’s report on solitary confinement for federal inmates, including those with mental illness]

By contrast, officials in six of eight state departments of corrections contacted by the inspector general said that they limit the length of time inmates with mental illness can be placed in restrictive housing. In 2015, according to the report, Massachusetts, Mississippi and New York had at least a 30-day limit, while three other states — Colorado, Maine and Pennsylvania — no longer place inmates with serious mental illness in restrictive housing.

The Bureau of Prisons does not track its housing of inmates in solitary confinement, nor does it always document inmates’ mental disorders, leaving the agency unable to ensure that inmates with mental illness are receiving appropriate care.

As of 2015, for example, only 3 percent of federal inmates were being treated regularly for mental illness. Yet an internal Bureau of Prison study suggested that about 19 percent of federal inmates had a history of mental illness, the report said. And a 2006 Bureau of Justice Statistics report concluded that 45 percent of federal inmates had symptoms or a recent history of mental illness.

“We found that the BOP cannot accurately determine the number of inmates who have mental illness because institution staff do not always document mental disorders,” the report by Inspector General Michael E. Horowitz said.

Horowitz’s report said that “equally concerning” was the finding that 13 percent of the inmates in the sample the investigators studied were released by the Bureau of Prisons directly back into the community after spending nearly 29 months in restrictive housing before release.

The Bureau of Prisons adopted a new mental health policy under President Obama in 2014, which increased the standards of care for prisoners with mental illness. But the inspector general’s investigation found that after the new policy was implemented, there was a 30 percent reduction in the number of inmates who receive regular mental health treatment.

“It appears that mental health staff may have reduced the number of inmates . . . who must receive regular mental health treatment because they did not have the necessary staffing resources to meet the policy’s increased treatment standards,” the report says.

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