Jackson's office released what they said was his doctor's statement. It read, "The Congressman is receiving intensive medical treatment at a residential treatment facility for a mood disorder. He is responding positively to treatment and is expected to make a full recovery."
- Healthbeat: Mood disorder: What is it?
Jackson's father, the Rev. Jesse Jackson, has been tight-lipped about his son's condition. He has been here attending the Rainbow PUSH Coalition's annual convention.
Medical experts say mood disorders can range from major depression or even bipolar disorder, and in a rarity for the normally open and engaging father of the congressman, the eldest Jackson did his best to avoid reporters at the convention.
He couldn't shake the cameras following him at the conference Thursday morning at the Hilton Hotel downtown. He stopped to talk only for a moment to plead once again for his son's privacy.
"We just hope that... we understand the interest in him, but I would hope that the zone of privacy would be respected," said Rev. Jackson.
The media has not learned where Jackson Jr. is being treated or who his doctor is.
"Mood disorder is as vague as exhaustion and it's obviously hiding some truth that's much more serious and much more damning to his political career," said ABC7 political analyst Laura Washington.
Jackson Jr.'s office noted in the statement that he is not being treated for alcohol addiction, despite rumors.
Congressman Jackson started his leave on June 10, but he waited two weeks to make it public. Until Wednesday evening, little detail had been officially released as to his condition.
The timing of his absence has raised questions in part because the South Side Democrat is facing an ethics investigation in the U.S. House connected to imprisoned former Illinois Gov. Rod Blagojevich.
"The most important thing is we don't know how long he will be out and when he's coming back," Washington said. "He has an obligation to his constituents to represent them. Is he going to be back in time for the election? Is he going to be back in time for the fall? These questions are serious questions that need to be answered and they related directly to his medical condition."
Calls for Jackson Jr. to give more of an explanation about his ailment keep coming, even from members of his own political party. Jackson's father asked everyone to be patient when it comes to releasing more details.
"We should not give a conclusion without adequate diagnosis and treatment," he said.