(AP) -- A state-commissioned University of Michigan study says about two-thirds of prisoners with severe mental illness get no treatment behind bars. The Michigan Corrections Department hired the university to conduct the study, which was mandated by a 2007 law.

Professor Brant Fries and his collaborators interviewed 618 inmates between May 1, 2008 and Sept. 30, 2009, and reviewed prison records. Michigan had about 48,000 prisoners then, and 30 percent - about 14,400 - had symptoms of mental illness. The researchers say 65 percent of them received no psychiatric treatment during the period studied.

Corrections spokesman Russ Marlan says department staffers are studying the recommendations in the 100-page study and will report back to state legislators.

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