PITTSBURGH — The parents of an inmate who hanged himself in a central Pennsylvania prison have sued the Department of Corrections for allegedly misusing solitary confinement to deal with mentally ill inmates.

Brandon Palakovic, 23, killed himself in July 2012 at the State Correctional Institution-Cresson, one of two older prisons closed last year so inmates could be moved to newer facilities. Before that happened, a U.S. Department of Justice civil rights investigation found solitary confinement was being overused on inmates with mental or intellectual disabilities.

“We found that Cresson often permitted its prisoners with serious mental illness or intellectual disabilities to simply languish, decompensate, and harm themselves in solitary confinement for months or years on end under harsh conditions in violation of the Constitution,” Roy L. Austin Jr., deputy assistant attorney general for civil rights, said in a statement in May 2013.

Those findings led the Justice Department to conduct a wider review of solitary confinement in Pennsylvania prisons, the results of which were announced in February. The Justice Department determined more than 1,000 prisoners with mental health problems had been in solitary confinement for at least three months, and nearly 250 for a year or more. At the time, Pennsylvania corrections officials said only 115 of its 50,000 inmates had severe mental illness or intellectual disabilities, but the Justice Department concluded state officials were underreporting those figures.

Renee and Darian Palakovic, who now live in Spring Hill, Tennessee, cite the Justice Department findings in their 25-page federal lawsuit filed late Tuesday.