Barrymore, who will be 43 tomorrow, is expected to stay at the pounds 200-a- night Marchwood Priory Hospital in Southampton "for a few weeks", according to his agent Anne Chudleigh. It is the second time he has been treated at the hospital, which also treated Arsenal soccer player Paul Merson for alcohol, gambling and cocaine problems.
Barrymore has just finished a triumphant live tour, Barrymore's Back!, and unveiled a pounds 1m one-hour television special to be shot in June.
But there have also been stories of disappointing ratings for the last series of Barrymore and a decision to pull the plug on the My Kind Of People series.
Critics have searched for signs of a slump in the entertainer's popularity since he sensationally admitted he was homosexual last year.
In the last few weeks, Barrymore has talked of continuing mental turmoil, and said he even feared his head would explode. He said he could not recapture the thrill he got onstage anywhere else, and had sought it through drink.
Ms Chudleigh said: "He is exhausted following a recent very hard tour and busy schedule. Hopefully the press and public will respect his privacy and extend the same privacy to his wife Cheryl."
Barrymore has frequently thanked Marchwood Priory's therapist Dr Austin Tate for changing his life after his stay there in 1993. But the following year he also underwent a month's strict drying-out at an exclusive clinic in the United States, recorded in detail in his book Back in Business.
His mental state has again been in the spotlight since he declared he was homosexual last summer. That revelation followed a series of increasingly lurid stories of bizarre behaviour and speculation about his sexuality.
A spokeswoman for Barrymore's company LWT said: "Michael's health and well-being are paramount and all his friends at LWT wish him a speedy recovery."Reuse content