The ACLU of Nevada released a 48-page study on the use of solitary confinement within the Nevada Department of Corrections system.

The study finds that corrections officials should audit the use of solitary confinement in the state’s prisons and adopt policies that end its use over extended periods and restrict it only to periods when there are security concerns.

The ACLU based its report on surveys of 281 inmates and public records requests. Last week, the deputy director for the corrections department told the Senate Judiciary Committee that the practices were unconstitutional and among the worst he’s seen.

The department announced in December that Nevada is one of five states selected to work with the Vera Institute of Justice on ways to reduce the use of solitary confinement.