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The doctor for Rep. Jesse Jackson, Jr., who has been missing from Congress on medical leave for the past month, finally issued a statement Wednesday evening, revealing that the seven-term congressman has been diagnosed and is being treated for a mood disorder, but did not disclose his current whereabouts.

"The Congressman is receiving intensive medical treatment at a residential treatment facility for a mood disorder," his physician wrote in a statement released by Jackson's office late Wednesday evening. "He is responding positively to treatment."

The statement also emphasized that information regarding his treatment is "protected by federal law under the privacy provisions of the Health Insurance Portability and Accountability Act of 1996." It did not disclose the name of the attending physician or the treatment center "in order to protect his continuing privacy."

Jackson's chief of staff, Rick Bryant, also went on the record Wednesday evening calling reports that Jackson was being treated for alcohol or substance abuse "not true."

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Mood disorders can range from mania to depression to bipolar disorder. The statement did not specify what is ailing Jackson beyond a "mood disorder.'

The mystery is fueling rumor and speculation throughout Washington and Illinois. Tuesday, a senior aide to Jackson who requested anonymity knocked down rumors that Jackson had attempted suicide. This was after the Chicago WLS talk radio show Roe & Roeper reported that sources indicated the Democratic congressman's mysterious absence was a result of a suicide attempt. Wednesday evening, NBC's Andrea Mitchell reported on 'Nightly News' that Jackson had been in Arizona seeking rehab for alcoholism and addiction.

A congressional source close to Jackson said the congressman is not likely to return to the House until after Labor Day and said he had spoken to Jackson as recently as "the last few days." Although he continues treatment at an inpatient facility, the congressman is not facing any life-threatening ailments, the source said.

Jackson has not voted in the House since June 8, missing more than 80 votes during the span of 11 days of legislative business. His absence was not explained as a medical leave until June 25, when his office said he was suffering from "exhaustion."

"That's what he has. He doesn't get a lot of sleep and he has sleep disorders. He's very energetic, running full-steam ahead, working six or seven days a week often and he's been doing that for a long time," a source close to Jackson told ABC earlier this week. "There's a great deal of pressure on him due to unfounded allegations [related to the ethics inquiry] and negative press onslaught against him that are not true, so it kinda all caught up to him. He needed downtime to get away from grind."

His office later issued a second statement that indicated he would be out for a considerable amount of time, and calls for an explanation of his absence have reverberated around the Halls of Congress this week. Even though Sen. Dick Durbin, D-Ill., and the No. 2 House Democrat Steny Hoyer, D-Md., both suggested Jackson should give an explanation of his absence, House Democratic Leader Nancy seemed is giving him the benefit of the doubt.

"The time is right [to fully disclose why he is gone] when Congressman Jackson has an evaluation of what his situation is and I'm sure then he will share it with his constituents," Pelosi, D-Calif., told reporters Wednesday afternoon. "Our prayers are with his family. I hope that we will hear soon that he is on the way to recovery. He's a valued Member of Congress, but the timing and the 'as soon as possible,' I think, is related not to my curiosity or anybody else's, but to his health care needs and as he figures out what that is."

"I feel sad that whatever the situation is that he finds himself having to be away from Congress but hope that we will see him back here soon again," Pelosi continued. "The timing relates to his knowledge of the situation and then he will share it with us. I feel quite certain."