Forcing inmates to spend prolonged periods in solitary confinement can produce harmful and lasting effects, according to multiple scientific sources.

One study of inmates serving time in the New York City jail system found that only 7.3% of jail admissions involved solitary confinement. However, 53% of inmates who tried to hurt themselves and 45% of cases where self-harm was potentially fatal happened to those whose admission included solitary. The research, published in the American Journal of Public Health, was based on 244,699 incarcerations from 2010 to 2013.

Jonathan Amos of BBC reported that an average of 80,000 prisoners are held in solitary at any given time in the U.S. This status can mean being isolated from all other people for upwards of 23 hours a day.

There are documented cases of inmates spending decades in solitary confinement.

Robert King was forced to remain in solitary for 29 years in the Louisiana State Penitentiary, also known as Angola Prison, for killing a prison guard. His conviction was eventually overturned. Another prisoner convicted of the same murder, Albert Woodfox, is still in Angola. He has been in solitary for 41 years.

Craig Haney, a professor at University of California, Santa Cruz, has studied hundreds of inmates like King who have endured solitary confinement.

“People who are in these units are in pain,” Haney told  BBC News. “This is not an experience that is easily tolerated psychologically, and people suffer in response to it.

He added: “The more common response is for people to become increasingly depressed, and to be enveloped by a sense of hopelessness.” Haney said many inmates in solitary confinement experience hallucinations and panic attacks.

Another expert, Professor Huda Akil of the University of Michigan, who studies the brain, says there is considerable data showing how harmful solitary confinement can be neurologically.

“We have a vast amount of knowledge about the brain and how it responds to each one of the elements [of solitary confinement]. The lack of physical activity, the lack of interaction with the natural world like sunlight, the lack of interactions with other human beings, the lack of visual stimulation, the lack of touch—each one of those has been studied not just in humans but in animal models such as rodents. And each one by itself is sufficient to change the brain and change it dramatically,” she told BBC News.

-Noel Brinkerhoff

To Learn More:

Solitary Confinement and Risk of Self-Harm Among Jail Inmates (by Fatos Kaba, Andrea Lewis, Sarah Glowa-Kollisch, James Hadler, David Lee, Howard Alper, Daniel Selling, Ross MacDonald, Angela Solimo, Amanda Parsons, and Homer Venters, American Journal of Public Health) (pdf)

Scientists Call Solitary Confinement 'Damaging and Unnecessary' (by Jonathan Amos, BBC News)

Twilight in the Box (by Shruti Ravindran, Aeon Magazine)

An End to "The Hole"?: 6 Signs that Solitary Confinement Reform Is Coming (by Nur Lalji, Yes Magazine)

Does Solitary Confinement in U.S. Prisons Qualify as Torture? (by Noel Brinkerhoff, AllGov)

Colorado Closes Empty $208 Million Solitary Confinement Prison (by Noel Brinkerhoff and David Wallechinsky, AllGov)