Within the prison walls is another world. In three shifts around the clock, the facility houses hundreds of inmates under the mechanized control of automated steel doors, steel batons, and the threat of something worse — solitary confinement.

Some 80,000 Americans are presently serving time in solitary confinement, according to an estimate from the Federal Bureau of Prisons, a disciplinary measure experts say is torturous to the healthy; never mind the criminally insane.

Since the 1970s, America has built the world’s largest prison system with approximately two million citizens, an individual population larger than nearly one-third of nations around the globe. The long war on drugs and a conservative shift in jurisprudence has shaped a country with only five percent of the world’s population, but a quarter of its jails. Here rose the “supermax” prison to house the nation’s most violent criminals, effectively sentencing men to life in solitary, with not much possibility of human contact.

Thomas Edward Silverstein is the nation’s longest-serving prisoner held in solitary confinement, an Aryan Brotherhood leader deemed highly dangerous by prison officials after murdering another three on the inside. In a jailhouse interview after his 1977 conviction, he once described the psychological torture of solitary confinement: “A slow constant peeling of the skin, stripping away of the flesh, the nerve-wracking sound of water dripping from a leaky faucet in the still of the night while you’re trying to sleep.”

Yet the momentum may be turning for prisoner rights advocates hoping to end a practice they describe as cruel but unfortunately all too common, a violation of the Bill of Rights. This week, New York was forced by a class-action lawsuit to promise an end to solitary confinement for women, minors, and the mentally disabled — reserving the punishment, presumably, for grown men deemed healthy for torture.

Similarly, Secretary Eric Holder’s Department of Justice has compelled Pennsylvania to close its state prison in Cresson after investigating allegations of misconduct under the newly enacted Civil Rights of Institutionalized Persons Act. The prison’s use of long-term and extreme forms of the punishment violated the Eighth Amendment rights of prisoners, the department found. As standard practice, prison officials there had kept inmates in solitary confinement for 22 to 23 hours per day for months and even years, in some cases.

“The department concluded that Cresson’s misuse of solitary confinement on prisoners with serious mental illnesses leads to serious harms, including mental decompensation, clinical depression, psychosis, self-mutilation, and suicide,” investigators wrote in a report.

Indeed, as many as a third of prisoners in solitary confinement may suffer from underlying mental illnesses, according to researchers at the University of California at Santa Cruz. And so common are symptoms of mental illness among prisoners held in solitary confinement that academic papers are now referring to a “special housing unit (SHU) syndrome.” Symptomatology include visual and auditory hallucinations, hypersensitivity to sound and touch, insomnia and paranoia, uncontrollable fear and anger, distorted sense of time, suicidality, and post-traumatic stress syndrome.

In America’s prisons and jails, institutional health care is often the first-line for diagnosing some of the millions lacking health insurance, including some four million former inmates newly eligible for Medicaid under the Affordable Care Act. In the evening after chow call, young men mill about the cell block in County Jail U.S.A., some playing cards but many waiting in line at the nurse’s station. Every other guy seems to be on some sort of antidepressant or mood stabilizer, and they all want weed.

Yet for those not under the proper spell, medicated or otherwise, any infraction — a minor or major disciplinary report, “D.R.” — may send them to the hole. Aside from the 25,000 federal prisoners serving solitary sentences in the “supermaxes” built to house them are another 55,000 inmates at state and local jails, according to advocacy group American Friends Service Committee. Locked within a small cell behind a solid steel door for most of the day, prisoners are subject to physical restraint and denied adequate medical and mental health treatment. They’re often denied reading materials.

Since the prison buildup in the 1970s, scores of thousands of Americans have served solitary time in supermaxes in 44 states, alongside the nation’s county jails. Though many rightly deserve to serve time, advocates such as the American Friends Service Committee say imprisonment in the U.S. should not involve torture. Increasingly, the Justice Department agrees.

Source: Kaba F, Lewis A, Glowa-Kollishsch S, et al. Solitary Confinement And Risk Of Self-Harm Among Jail Inmates. American Journal of Public Health. 2014.