Just hours after Democratic leaders in Congress ratcheted up pressure on Jackson to reveal more information, his office released a brief statement from his doctor on Wednesday saying the Chicago Democrat was receiving "intensive medical treatment at a residential treatment facility for a mood disorder."
But it offered no details about Jackson's whereabouts or even the name of the doctor, citing federal privacy laws.
Several experts said that based on the doctor's use of the term "mood disorder," they believed Jackson might be suffering from depression. But the statement did not elaborate on his condition and rejected claims that the 47-year-old congressman was being treated for "alcohol or substance abuse."
"He is responding positively to treatment and is expected to make a full recovery," the statement said. His spokesman declined to elaborate.
When Jackson's medical leave was first announced — two weeks after it began on June 10 — his office said he was being treated for exhaustion. Last week his staff said his condition was worse than previously thought and required inpatient treatment, saying Jackson had been privately battling emotional problems. The office has remained mum on details.
The timing of the leave has invited scrutiny, coming as Jackson faces an ethics investigation in the U.S. House connected to imprisoned former Illinois Gov. Rod Blagojevich. Days before Jackson's office announced his leave, a fundraiser and family friend also involved in the probe was arrested and charged with unrelated medical fraud charges.
The Associated Press on Wednesday interviewed several physicians who didn't have firsthand knowledge of Jackson's condition but said the term "mood disorder" typically refers to depression or bipolar disorder, which used to be known as manic depression.
Dr. Daniel Yohanna, vice chairman of the Department of Psychiatry and Behavioral Neuroscience at the University of Chicago, said depression is more common and affects about 5 percent of men at some point in their lives. Symptoms can range from sleep disturbance and appetite problems to hopelessness and thoughts of suicide, though cure rates are very high, he said.
"It could come out of nowhere, it runs in families, you could have a genetic predisposition, or it can come after a difficulty in your life," Yohanna said. "Once it gets rolling it's hard to stop it on your own."
Ian Gotlib, a professor of psychology at Stanford University, said depression is generally treated on an outpatient basis. But he said that if doctors were concerned about the safety of the patient or if the disorder were severe enough, they could recommend inpatient treatment.
"The good news is that it's clearly treatable," Gotlib said, adding that counseling and prescription drugs would be likely for inpatient treatment and that it could take weeks.
It's unclear whether Wednesday's statement would temper the mounting demands for full disclosure of the congressman's ailment.
Before Jackson's statement was released, Democratic leaders in the U.S. House joined Jackson's colleagues and constituents in urging the congressman to provide a public update about his condition. House Leader Nancy Pelosi, when asked about Jackson, said she hoped he would have "the appropriate evaluation so he can share that information."
Rep. Steny Hoyer of Maryland, the No. 2 Democrat in the U.S. House, said Wednesday that Jackson wasn't in "an unusual circumstance."
"People get sick, and when people get sick, they miss work. Everybody in America understands that," Hoyer said. "But I think the family would be well advised to give his constituents as much information as is appropriate."
Fellow Illinois Democrats Sen. Dick Durbin and Rep. Luis Gutierrez have called it Jackson's responsibility as a public official to disclose details. Jackson's little-known opponents in the November election have spoken out on the same issue, and some voters in his district have asked questions.
Durbin was unavailable for comment Wednesday evening after the Jackson office's latest statement.
Jackson spokesman Rick Bryant has said relatives requested Jackson's location be kept private, and his family has been unusually reticent on the issue. His wife, Chicago Alderman Sandi Jackson, has said little. And his father, civil rights leader Rev. Jesse Jackson Sr., has called it a private issue and repeatedly declined to give details.
The pending House Ethics Committee investigation is focusing on allegations that Jackson discussed raising money for Blagojevich's campaign so the then-Illinois governor would appoint him to President Barack Obama's vacated U.S. Senate seat. Blagojevich is serving a prison sentence for corruption. Jackson has denied the claims.
Jackson also allegedly directed a fundraiser, Raghuveer Nayak, to buy plane tickets for a woman described as Jackson's "social acquaintance." Jackson and his wife have called that a personal matter.
Nayak was the fundraiser arrested and charged with the unrelated medical fraud charges. He has pleaded not guilty.
At Blagojevich's 2010 corruption trial, prosecutors said another Blagojevich fundraiser was ready to testify that Jackson instructed Nayak to raise money for Blagojevich's campaign to help him secure the Senate seat. The same witness later testified he attended a meeting with Jackson and Nayak.
Jackson was not charged and has repeatedly denied wrongdoing.
Jackson faces a Republican and independent candidate in November, though he's widely expected to win re-election. He first won office in a 1995 special election and has easily won each race since. Jackson's district includes parts of Chicago and some suburbs but was expanded during the last redistricting process to include less familiar territory further south of the city.
Associated Press writers Donna Cassata in Washington and Jason Keyser in Chicago contributed to this report.
Copyright 2012 The Associated Press.