DMX returned to prison on Dec. 16 after pleading guilty to violating the terms of his probation, but the Yonkers rapper is now being held in a mental-health unit of Arizona's Alhambra Prison Complex.

DMX -- real name Earl Simmons -- was admitted to the Flamenco Mental Health Unit at the Arizona State Prison on Dec. 20. During his sentencing earlier this month, Judge Christine Mulleneaux told the troubled rapper that she believes he has "an undiagnosed mental condition," which might be bi-polar disorder. DMX was arrested for possession of Oxycontin in November and was suspected to be under the influence of cocaine, in addition to driving on a suspended license. His manager Nakia Walker says that he will be forced to remain in the mental-health unit without visitors, for at least 30 days.

The rapper was served a year long sentence (minus 113 days served) for breaking his probation. This marks DMX's 13th time behind bars, after more than 25 arrests over the past decade. He celebrated his 40th birthday on Dec. 18.

Watch DMX's 'Slippin''