THE PHYSICAL stresses of solitary confinement are bad enough. In the United States, conditions can include windowless cells, nearly inedible food served through door slots, extreme heat and cold and almost no time to exercise or wash. The psychological costs of extreme social isolation are worse; for many, in fact, they are unbearable. Solitary confinement can cause or exacerbate psychosis, hypertension, panic attacks, self-mutilation and suicide. Those who cope more effectively still may deteriorate in less obvious ways as their brains and bodies waste away. Tens of thousands of U.S. prisoners are living, some for years at a time, in such conditions.

Damon Thibodeaux was wrongfully convicted of rape and murder. He now recounts that, near the beginning of his 15 years in solitary, he wanted to commit “suicide by state,” ending his legal fight and allowing Louisiana authorities to execute him. Isolation, he told a Senate committee Tuesday, kills “bit by bit, day by day.”

“I thought it would be better to end my life as soon as I could and avoid the agony of life in solitary,” he said. His lawyer persuaded him to press his case, and he eventually prevailed.

Separating prisoners from human contact is abusive in all but the most extreme circumstances. Yet, as Rick Raemisch, the head of Colorado’s Department of Corrections, told the committee, the practice is “incredibly overused,” often to punish minor infractions of prison rules.

In Texas, inmates sent to solitary spend an average of four years there, reported Marc Levin of the conservative criminal justice reform group Right on Crime. Texas, though, is at least reviewing its practices. That might be because isolating prisoners is expensive — costing something like twice as much as keeping them in the general prison population. Or it might be because releasing psychologically damaged people from prison can produce disastrous results. Regardless of motive, cutting the use of solitary is the right thing to do.

A few other states have made strides in recent years. New York just announced that it would restrict or eliminate solitary confinement for women, minors and the mentally ill, as well as adopt new guidelines on applying the punishment to others. Maine and Mississippi have drastically reduced the number of prisoners they keep in solitary; they report encouraging results. Mr. Raemisch recently shut Colorado’s administrative segregation facility, and Illinois closed its supermax prison.

Sen. Richard J. Durbin (D-Ill.) on Tuesday called on prison systems to follow New York’s lead. That’s the least prison authorities can do. To go further, Mr. Levin recommended eliminating rules that deny or restrict reading materials for isolated inmates, creating a range of punishments short of solitary that would more effectively and more humanely deter misbehavior and training prison staff to deal sensibly with prison conflicts and mentally ill inmates. Effectively applied, those measures would begin to reduce the number of people subjected to the hell of solitary without harming prison order.