WASHINGTON -- Rep. Jesse Jackson Jr., who hasn't been seen on Capitol Hill since late May, hopes to return work Monday after checking out of the Mayo Clinic where he was treated for bipolar depression, his office said.

Monday is the first day back for Congress after summer recess.

Rick Bryant, the chief of staff in Jackson's congressional office, told CNN on Friday that the Illinois Democrat had left the prestigious Minnesota medical facility and was back in the nation's capital.

Asked at the time whether Jackson would be back at work, Bryant said, "We hope."

In early July, the congressman's office announced he was "receiving intensive medical treatment at a residential treatment facility for a mood disorder." A few weeks later, his office said he was undergoing an "extensive inpatient evaluation for depression and gastrointestinal issues" at the Mayo Clinic.

Jackson's wife, Sandi, said in August that her husband had "good days and bad days" and doctors were increasing his depression medication to "therapeutic levels."

The congressman's father -- the Rev. Jesse Jackson, a well-known civil rights leader -- told The Huffington Post last month that when he visited his son in Washington in June, he learned the junior Jackson hadn't slept for three days.

What the family thought was exhaustion, the elder Jackson said, was "something much deeper, much broader, and it lasted longer."

Jackson's illness comes as the House Ethics Committee is examining allegations that, in 2008, he or one of his associates offered to raise money for then-Illinois Gov. Rod Blagojevich in exchange for Jackson being appointed to the Senate seat vacated by Barack Obama after he was elected president.

The congressman has maintained his innocence and pledged to continue to cooperate with authorities.

As for Blagojevich, he was convicted last year on corruption charges in connection with efforts to profit from appointing the successor to the Senate seat.

A day after visiting Jackson at the Mayo Clinic last month, longtime friend and former U.S. Rep. Patrick Kennedy said he suspected that "stress in (Jackson's) life, particularly because he's under investigation," may have set off his depression.

Kennedy struggled with addiction and bipolar disorder and is a mental health advocate.

"Many of us have genetic predisposition to cancer, heart disease or, in this case, mental illness, but they often get triggered by environmental factors," said Kennedy, the son of the late Sen. Edward Kennedy. "In mental illness, stress is an environmental factor and clearly, I think, has been a factor in his succumbing to this outbreak of his bipolar disorder."

Bipolar disorder is a treatable condition that affects parts of the brain controlling emotion, thought and drive, the Mayo Clinic says. Many Americans suffer from it, and it is most likely caused by a complex set of genetic and environmental factors, it says.

Medical experts are still weighing whether gastric bypass surgery that Jackson underwent in 2004 for weight loss might have helped trigger his depression, his wife said. The Mayo Clinic said that type of surgery is increasingly common in the United States and can change how the body absorbs food, vitamins, nutrients and medications.