A new report from the corrections watchdog has found 29 percent of prisoners spent time in complete isolation in 2020 and 2021.
Prisoners were left in restrictive spaces with little to do, and the report suggests for many of them it was for months or years.
It says the psychological effects on those in isolation, such as depression and paranoia, can be irreversible.
Tracey McIntosh is a professor of Indigenous Studies at Auckland University, who's spent time working with prisoners.
She spoke to Gyles Beckford.
