That has been pretty much an accepterds fact pf psychology since the 1960s, at least. I know it was brought up in some of the Psych and Special Ed classes I took in 1970-77. Sorry I can't cite a study right nopw, but sensory depravation can be used to induce a condition similar to schizophrenia. You start to halucinate after a while.
There's a growing body of research on the deprivations associated
with solitary confinement. This is in use all over the world in normal operations of prisons - we're not just talking about "enemy combatants" here.
Some of the side effects of long-term isolation include: higher rates of recividism, long-lasting psychological ailments, an inability to socialize, increased rage reactions to what would appear to be innocuous triggers.
This New Yorker piece was quite excellent regarding this subject:
"It’s an awful thing, solitary,” John McCain wrote of his five and a half years as a prisoner of war in Vietnam—more than two years of it spent in isolation in a fifteen-by-fifteen-foot cell, unable to communicate with other P.O.W.s except by tap code, secreted notes, or by speaking into an enamel cup pressed against the wall. “It crushes your spirit and weakens your resistance more effectively than any other form of mistreatment.” And this comes from a man who was beaten regularly; denied adequate medical treatment for two broken arms, a broken leg, and chronic dysentery; and tortured to the point of having an arm broken again. A U.S. military study of almost a hundred and fifty naval aviators returned from imprisonment in Vietnam, many of whom were treated even worse than McCain, reported that they found social isolation to be as torturous and agonizing as any physical abuse they suffered.
And what happened to them was physical. EEG studies going back to the nineteen-sixties have shown diffuse slowing of brain waves in prisoners after a week or more of solitary confinement. In 1992, fifty-seven prisoners of war, released after an average of six months in detention camps in the former Yugoslavia, were examined using EEG-like tests. The recordings revealed brain abnormalities months afterward; the most severe were found in prisoners who had endured either head trauma sufficient to render them unconscious or, yes, solitary confinement. Without sustained social interaction, the human brain may become as impaired as one that has incurred a traumatic injury.
...
After a few months without regular social contact, however, his experience proved no different from that of the P.O.W.s or hostages, or the majority of isolated prisoners whom researchers have studied: he started to lose his mind. He talked to himself. He paced back and forth compulsively, shuffling along the same six-foot path for hours on end. Soon, he was having panic attacks, screaming for help. He hallucinated that the colors on the walls were changing. He became enraged by routine noises—the sound of doors opening as the guards made their hourly checks, the sounds of inmates in nearby cells. After a year or so, he was hearing voices on the television talking directly to him. He put the television under his bed, and rarely took it out again.
One of the paradoxes of solitary confinement is that, as starved as people become for companionship, the experience typically leaves them unfit for social interaction. Once, Dellelo was allowed to have an in-person meeting with his lawyer, and he simply couldn’t handle it. After so many months in which his primary human contact had been an occasional phone call or brief conversations with an inmate down the tier, shouted through steel doors at the top of their lungs, he found himself unable to carry on a face-to-face conversation. He had trouble following both words and hand gestures and couldn’t generate them himself. When he realized this, he succumbed to a full-blown panic attack.
...
Craig Haney, a psychology professor at the University of California at Santa Cruz, received rare permission to study a hundred randomly selected inmates at California’s Pelican Bay supermax, and noted a number of phenomena. First, after months or years of complete isolation, many prisoners “begin to lose the ability to initiate behavior of any kind—to organize their own lives around activity and purpose,” he writes. “Chronic apathy, lethargy, depression, and despair often result. . . . In extreme cases, prisoners may literally stop behaving,” becoming essentially catatonic.
Second, almost ninety per cent of these prisoners had difficulties with “irrational anger,” compared with just three per cent of the general population.* Haney attributed this to the extreme restriction, the totality of control, and the extended absence of any opportunity for happiness or joy. Many prisoners in solitary become consumed with revenge fantasies.
