More than half of the inmates in U.S. prisons suffered from mental problems, says the Human Rights Record of the United States in 2006 issued here on Thursday.

About 56 percent of inmates in state prisons, 64 percent in detention houses and 45 percent of federal prisoners had received treatment or shown symptoms of various mental diseases, including serious melancholia, mania and hallucination, said a report issued by the U.S. Justice Department.

The report also said more than 1.5 million inmates are released each year carrying life threatening contagious diseases.

The United States has nearly 60 "super-security prisons", housing about 2,000 prisoners. The inmates are jailed in 6-square-meter wards, which are sound proof with lights and monitors on around the clock. Such prisons have left many prisoners with mental diseases.