Some prisoners became so disoriented they began to question their own existence.

Another inmate said that the hour or so he had spent in the interview was “the most I’ve talked in years.”

The California Department of Corrections and Rehabilitation, citing the continuing litigation, declined to comment on the lawsuit or on the reports of Dr. Haney or other expert witnesses for the plaintiffs. But since the lawsuit was filed, the department has moved many inmates who had been in isolation at Pelican Bay for more than a decade to other settings. All but two of the 10 inmates originally named as plaintiffs in the lawsuit are now in other facilities, according to Jeffrey Callison, a department spokesman.

In an interview, Dr. Haney said that he was especially struck by the profound sadness that many of the inmates he interviewed seemed to carry with them.

“The weight of what they had been through was apparent on them and in them,” he said.

“They were grieving for their lost lives, for their loss of connectedness to the social world and their families outside, and also for their lost selves,” he said. “Most of them really did understand that they had lost who they were, and weren’t sure of who they had become.”

‘There Is No Other Reality’

An estimated 75,000 state and federal prisoners in the United States are held in solitary confinement, according to prison experts. Most spend 23 or more hours a day in their cells, allowed out only for showers, brief exercise or activities like medical visits.