Over the past six years, the number of solitary beds in New York City’s Rikers Island jail complex has grown by 61.5 percent, according to a study commissioned by the city’s Board of Correction. Bebeto Matthews / AP

"Since prolonged solitary confinement can cause symptoms of mental illness to appear even in previously healthy individuals, we strongly recommend against imposing it as a punishment for a predetermined duration even on those inmates not deemed to be mentally ill," said New York University psychiatrist and lead author James Gilligan.

The report recommends eliminating the use of solitary as a punishment for mentally ill inmates in favor of partnering with a teaching hospital to provide intensive therapeutic services. The study was commissioned by the New York City Board of Correction, which has a watchdog role over the city's Department of Correction (DOC).

About 40 percent of Rikers' 12,200 inmates have some kind of mental health diagnosis, and about a third of those have so-called serious mental illnesses such as schizophrenia or bipolar disorder. Of the roughly 800 inmates in solitary at any given time, just over half are mentally ill.

The wide-ranging review, obtained by The Associated Press through a Freedom of Information Act request, is critical of the city's use of solitary as punishment for inmates who by the very nature of their mental illnesses are more prone to breaking jailhouse rules.

Mentally ill inmates in New York City's most notorious jail are too often placed in solitary confinement — in some cases for thousands of days at a time — a practice that coincides with an increased rate of violence inside the jail, according to an independent review of mental health standards at Rikers Island, a 10-facility lockup on a 400-acre island in the East River.

Guards at the California State Prison, Corcoran, routinely pepper-spray mentally ill inmates to get them to leave their cells so guards can give them medication or move them to new cells, according to a lawsuit.

New York is not the only city to grapple with how to manage a growing population of mentally ill inmates — and its increased use of solitary confinement mirrors trends in other big cities such as Chicago and Los Angeles, Gilligan said.

As mental institutions have closed over the past 50 years, prisons have absorbed many more of the mentally ill. A 2010 survey by the nonprofit Treatment Advocacy Center and the National Sheriffs' Association found that there were more than three times as many seriously mentally ill people in jails and prisons than there were in hospitals.

Solitary, also called "the hole" or "the bing," is doled out punitively when inmates break certain rules, seriously assault someone or attempt to hurt themselves. It can be used by prisons to isolate volatile inmates as a form of suicide prevention or as a form of protective custody.

The review focused on Rikers Island, as the Board of Correction pushes for reforms to the way the mentally ill and adolescents are jailed. It described some Rikers units as filthy and vermin-ridden, with cracked linoleum that inmates break off and use to cut themselves.

Over the past six years, the number of solitary beds in Rikers Island has grown by 61.5 percent, from 614 to 998.

Six inmates have spent more than 1,000 days in 22-hour isolation, and one has spent nearly 3,000 days in the Mental Health Assessment Unit for Infracted Inmates (MHAUII), a two-tiered housing area where inmates are placed in suicide-resistant single-occupancy cells with cinder-block walls and food slots through which they can be handcuffed and served meals. An assistant commissioner for the city's Department of Health and Mental Hygiene once called such areas "parking lots for people with mental illness."

Most significantly, the report tied this increased use of solitary with rising overall incidents of violence at Rikers.

Use-of-force incidents by correction staff per 100 inmates have more than tripled from seven in 2004 to 24.7 in the first six months of this year. The number of self-mutilations and suicide attempts by Rikers inmates increased by 75 percent from 2007 to 2012. Mentally ill inmates account for about 60 percent of assaults on staff and fellow prisoners that result in serious injury, according to the city's DOC.

In August 2012, a mentally ill 25-year-old burglary suspect named Jason Echevarria died after consuming a toxic soap ball while jailed in a MHAUII cell as he awaited trial. His father claims in a $20 million lawsuit that Echevarria was denied medical attention by guards who walked by his cell as he died.

City officials said the Board of Correction review didn't provide a proper context for reform efforts initiated since 2009. They also scoffed at the notion that rising levels of violence could be tied to an increase of punitive segregation beds.

"It was DOC who saw this striking growth in the percentage of the mentally ill in the jails, and we rang the bell," city Correction Commissioner Dora B. Schriro said in an interview with Reuters.

Schriro said she temporarily increased the number of solitary beds in 2010 by more than 200 as a way to address a backlog of solitary sentences, while at the same time instituting reforms. The department has developed new sentencing guidelines, introduced nonsolitary punishments like timeouts for nonviolent infractions, and recently opened 80 beds in two new dormitory-style units for mentally ill inmates at Rikers facilities called Clinical Alternative to Punitive Segregation. The MHAUII units are to be closed permanently this fall, Schriro said.

The Associated Press