The use of restrictive housing (“solitary confinement”) in U.S. prisons is becoming less common, yet 61,000 prisoners were still held in these conditions in the fall of 2017, including more than 4,000 persons diagnosed with a serious mental illness.

These were two key data points included in a report released on Oct. 10 by the Association of State Correctional Administrators (ASCA) and the Arthur Liman Center at Yale Law School.

In surveys sent to U.S. correctional facilities to gather data for the report, restrictive housing was defined as “separating prisoners from the general population and holding them in their cells for an average of 22 or more hours per day for 15 or more continuous days.”

This definition aligns with the U.S. Department of Justice’s report and recommendations on this practice that were released in January 2016.

Of the prison systems contacted, 46 responded to the ASCA-Liman survey. Of these, 43 sent information about restrictive housing, reporting a total population of more than 1.08 million prisoners, with nearly 50,000 in restrictive housing.

This data accounts for 80 percent of the U.S. prison population at the time of the survey. Estimating for the other correctional institutions that didn’t provide data, around 61,000 prisoners were in restrictive housing conditions in the fall of 2017.

“Thirty jurisdictions reported when they began to track how long people had been in restrictive housing. Some jurisdictions began tracking this information as recently as 2017. Within the responding jurisdictions, most people were held in segregation for a year or less,” the ASC-Liman report said. “Twenty-five jurisdictions counted more than 3,500 individuals who were held for more than three years. Almost 2,000 of those individuals had been there for more than six years.”

The report cited studies indicating that up to 33 percent of persons in U.S. prisons could have a serious mental illness, noting “a consensus has emerged that individuals identified as having [a] serious mental illness should not be placed into restrictive housing.”

In one of five essays from prison administrators included in the report, Rick Raemisch, executive director of the Colorado Department of Corrections, noted that their system had “stopped manufacturing or multiplying mental illness by the overuse of segregation.”

Yet, 6.6 percent (4,000) of the 61,000 prisoners in restricted housing were reported by correctional institutions as having a serious mental illness.

More males than females were in restricted housing. Black, Hispanic and Native American prisoners accounted for a higher percentage of persons in restricted housing situations than they did as a percentage of the total prison population. The reverse was true for white inmates.

“Consensus has emerged about the harms to individuals held in deeply isolating conditions; to staff working in restrictive housing; and to community safety,” the report stated. “The reiterated theme is that 22 hours or more of confinement in a small cell for days on end is unwise, unjust and inefficient.”

The full ASCA-Liman report is available here.