Here’s what it’s like to be in solitary confinement in a supermax prison—you are locked into your 8- by-10-foot cell for 23 hours per day, where the lights are on all the time. There are no windows in your cell to let in sunlight. Your only view is the window in the cell door that looks out onto a sterile cellblock.

When you are allowed out for one hour of recreation per day, you must first be strip-searched. Then you are shackled hand and foot and taken by two guards to a small wire cage that is your “exercise” yard. You are not allowed to talk to the guards, or to the other prisoners who may be exercising in the cages next to you. You are then shackled again, and led back to your cell. All meals are served to you through a slot in your cell door. If you’re very lucky, you will be allowed outside twice a week where, shackled to a table in the middle of the cellblock, you will perform menial labor, like wrapping packets of sporks and salt in napkins that will be placed in the prisoners’ meal trays.

Imagine living like this year after year after year.

“I don’t think solitary as it currently exists, the lack of any human contact of any sort, is necessary in any case,” says Kristin Jacobson, whose film Solitary, shot at the Red Onion State Prison in Wise County, Va., debuts this week at New York’s Tribeca Film Festival and will be broadcast later this year on HBO. “This is the United States. We have a Constitution, we condemn the abuse of human rights elsewhere, and just because you’ve committed a crime you have not given up your rights as a human being.”

Solitary confinement has, in fact, been part of American penology since at least 1829, when Philadelphia’s Eastern State Penitentiary housed prisoners in isolation, hoping that the silence would encourage them to think about their foul deeds and become truly penitent (thus the term “penitentiary”).

But the practice really took off in the 1980s, when harsh drug laws, gang activity and mandatory sentencing saw the prison population increase dramatically. “Solitary grew rapidly just about everywhere; it tracks with the growth in the prison population, and prison overcrowding,” says Jean Casella of Solitary Watch, a Web-based organization providing research and news about solitary confinement in the U.S.

“You had all these people,” says Casella, “and this was one way to control them.”

It is estimated there are now as many as 80,000 prisoners in some form of segregated confinement, nearly a third of them in supermax prisons.

Yet studies have shown that extended stays in solitary can create severe psychological damage, causing prisoners to have hallucinations, panic attacks, severe paranoia, and other symptoms.

“Social interaction is a fundamental need, and when it’s withdrawn, our brains experience that in the same way physical pain is experienced,” says Alexis Agathocleous of the Center for Constitutional Rights. “A prolonged period of isolation is a form of social death.”

That’s certainly the case with the prisoners in Solitary, who describe their experience as being “buried alive,” and feeling “this rage that builds and builds,” to the point where they express extreme frustration and anger over small things like not having any salt in their food tray.

Plus, solitary confinement can be extremely expensive. Single-cell confinement and enhanced security mean construction costs of supermax prisons can be two to three times that of a conventional facility. Add in the necessary extra staffing and it has been estimated that the cost of housing a prisoner in solitary is two to three times that of housing a prisoner in the general population.

And there’s this: Despite the conventional wisdom that solitary is for the worst of the worst, or to isolate prisoners for their own protection, some prisoners are put in solitary for minor offenses like having too many postage stamps (considered contraband), refusing to eat all the food on their tray, cursing a guard or refusing an order—any kind of order.

Yet attitudes toward solitary, and its practice, are slowly beginning to change. In 2011 Juan Mendez, the UN Special Rapporteur on torture, called for all countries to ban the practice except for very special circumstances, and added that solitary confinement beyond 15 days should be strictly prohibited.

Last year, following a 2013 hunger strike by 30,000 prisoners in the California penal system protesting the abuse of indeterminate solitary confinement, the state settled the case of Ashker vs. Brown, a 2012 lawsuit filed by a group of inmates who had spent more than a decade in isolation in Pelican Bay, a notorious supermax. The state agreed to end indeterminate length sentences in solitary, released almost all prisoners who had spent more than 10 years in isolation into the general population, and promised not to place any prisoners in solitary for gang membership without other reasons.

And this past January, President Barack Obama announced a series of changes designed to reduce the use of solitary in the federal prison system. These include banning solitary for juveniles, pregnant women and for low-level offenses, expanding mental health treatment and increasing the amount of time inmates can spend outside their cells. The changes also plan to reduce maximum solitary for first-level offenses from one year to 60 days.

Not that change on the federal level is going to do much for Lars, a lifer currently in the Red Onion supermax for an escape attempt, or Dennis, convicted of armed robbery and now segregated for 17 years for cutting a warden. Change on the state level varies wildly, often depending on the vagaries of prison administrators and corrections officer unions, who often see more liberal policies as a physical threat to their members. In the institutions promoting some sort of reform, “there are positive incentives,” says Casella, “like visits, TV time, more time out of cell for recreation, time in the day room. One of the reasons for these programs is not just to prove these guys can go about their business without violent acts, some of these guys have been in solitary for 10 years. There are mental health components necessary to transition people back into the system.”

“The last four or five years we have seen this sea change in attitudes about solitary,” adds Agathocleous. “People who are incarcerated have advocated for themselves to highlight their plight. The will of prisoners to tell their stories has educated the media and the public. And we have prison administrators starting to speak out.”

And yet, reformers in the field recognize that a significant percentage of the public is more likely to ask, “Who cares about these lowlifes?” A recent poll in the Jersey Journal, for example, found that over 50 percent of respondents disagreed with Obama’s proposal that solitary for juveniles and low-level offenders be banned.

Still, as Johnson puts it, “something like 90 percent of prisoners are released one day, and it’s a public safety crisis if you’re making people worse in prison.” Which means, notes Casella, “these are public safety issues, not humanitarian ones. What would happen if you locked a dog in a cage for years on end, then let it out and expected it to be a nice family pet? These people need more treatment than anything else, not isolation and sensory deprivation.”

Or, as Randall, one of the prisoners in Solitary, puts it: “All [solitary] is doing is turning us into caged animals. Life ain’t worth it without hope.”