From the outside, solitary confinement seems to make sense as punishment for a prisoner's bad behavior or as a way of protecting them from other inmates. But on the inside, the psychological effects of living without normal stimulus or human conversation can drive prisoners to hallucinate, act violently or commit suicide.
It's even worse for young prisoners whose brains are still developing, experts say.
President Obama this week banned the practice of solitary confinement for youths under 18 being held in federal prison facilities, citing scientific studies of its dangers.
Because young people's brains are still developing, the effects of solitary are even worse, according to Stuart Grassian, a Boston-area psychiatrist who has written extensively on juveniles in solitary confinement and consulted with states on their prison policies.
"Adolescence is a period of time where there is a marked increase in the amount of emotional energy in the system; the limbic system is aflame," Grassian said. "Yet the judgment, the control, the inhibition of emotion and behavior hasn't occurred yet. During the process of adolescence up through a person's early 20s there's a process of emotional and neural maturation, pruning of neurons, pathways in the brain. As a result, juveniles are particularly vulnerable to experience out-of-control emotions and reacting to them."
Grassian says that youths up to the early 20s often act out when sent to any kind of juvenile detention. That in turn, often puts them in trouble with prison officials, who then put them in solitary confinement thinking that it will stop their acting-out behavior.
"That paradigm only applies to a rational actor who is able to make judgments on the likely consequences, risks and benefits," said Grassian, who has interviewed several hundred prisoners confined to solitary. "What we are talking about are kids who are unable to use that kind of algorithm to figure out what they are going to do. They just react."
Once they are sent to solitary cells, they begin to experience a host of psychological issues from hallucinations, delusions, loss of spatial perception, paranoia, hypersensitivity to noises, and many symptoms common to attention deficit disorder, he added.
"They become more jumpy, more impulsive, they react to stimuli in more exaggerated ways," he said. "You end up with a vicious cycle of out-of-control behavior, impulsivity, and once a kid ends up in that vicious cycle it's impossible to get out of it."
Kids who spend a longer time in solitary are at a great risk to harm themselves, or commit suicide.
Some of these psychological effects fade after the person rejoins the rest of the prison population. But even after they get out, some young people find they are permanently scarred.
"As people become less capable of managing stimulation over time, they have a difficult time managing social stimulation," Grassian said. "People who used to be gregarious become loners. They can't tolerate noise or people."
President Obama cited the case of a 16 year old who spent several months in solitary confinement in New York's Riker's Island Jail for stealing a backpack. After months of trial delays, he was found innocent. But he was unable to handle his adjustment back to society and killed himself at age 22.
Over the last 30 years, solitary confinement has become the default practice for dealing with many problems in running a prison, according to Amy Bettig, senior staff counsel with the ACLU's National Prison Project.
"I have talked to kids in adult prisons and jails and they purposely get in trouble because they are so afraid of getting raped and beaten up by adult prisoners," Bettig said. "But when they get into solitary they lose their minds."
Grassian said that the developing brain is kindling, or establishing neural pathways for behaviors and the reward system. When the system is corrupted by the stresses of solitary confinement, it often remains that way.
When some juveniles are removed and placed in a psychiatric unit, many are able to rebound, according to Grassian, however the costs to society are great.
"Solitary costs so much more, and for 95 percent of the population you have created the worst possible situation," he said. "The chance of them making it in society becomes so much less."
Obama's order does not affect juveniles held in state or local prisons, where most are placed by judges. Both Grassian and Bettig said they believe the executive order could lead to changes on the state level. Already, New York, Massachusetts and Missouri ban the practice of putting juveniles in adult prisons in solitary confinement.