The New York City Board of Correction released a report last week that documents the stories of three adolescents who were sentenced to more than 200 days in isolation on Rikers Island.

Each of the teens, who were 17 and 18 years old when they were interviewed by the Board, had been diagnosed with a severe mental illness—two with bipolar disorder; one with depression. They had been placed in what's known as 'punitive segregation' for behavioral infractions like fighting or assaulting a corrections officer.

Once in segregation, they spent 23 hours per day alone in their cells, according to the report. Their recreation took place in individual outdoor cages. They weren't allowed to attend school and received no special education services. The majority of their appointments with mental health providers were conducted through cell doors—the adolescent stayed locked inside while the clinician stood in the hallway.

One of the adolescents described the isolation unit as a dungeon. Another talked about the repetitiveness of his days: "Sometimes you just sit there, to just sit there, to just sit there, for hours... hours of just sitting there... I talk to myself and answer myself now, and, all of a sudden, I start doing karate moves in my cell, and I don't even do karate. This is crazy. I really feel like I'm bugging out in that cell."

Adolescents, ages 16 to 18, make up about five percent of the average daily population on Rikers Island, according to the report. In a one-day snapshot conducted by the Board of Correction, nearly 27 percent of the 586 teenagers on the Island were in punitive segregation. More than 70 percent of those adolescents were diagnosed as mentally ill.

New York is one of just two states in the country to automatically send children as young as 16 though the adult criminal just system. Read here for more information on efforts to raise the age of criminal responsibility.

Abigail Kramer is a public policy journalist at the Center for New York City Affairs and the parent of a 6-year-old in Brooklyn. She writes regularly for Child Welfare Watch.