Rep. Jesse Jackson, Jr. suffering from bipolar disorder

(CBS/AP) Rep. Jesse Jackson, Jr., D-Ill., is undergoing treatment for Bipolar II depression, the Mayo Clinic announced Monday.

Jackson has been out of the public eye since June 10 and is currently being treated at the Mayo Clinic in Rochester, Minn.

"Following extensive evaluation, Congressman Jesse Jackson, Jr. is undergoing treatment for Bipolar II depression," the clinic's statement read. "Congressman Jackson is responding well to the treatment and regaining his strength.

"Congressman Jackson has asked Mayo Clinic to distribute this information on his behalf. He and his family remain grateful for support and prayers offered and received on his behalf."

It's unclear when Jackson Jr. will be released, though a report last week suggested he's expected back home "within a matter of weeks."

Earlier this month, Jackson's office announced he was at the Mayo Clinic being treated for depression, following a transfer from the Sierra Tucson Treatment Center in Arizona.

Jackson, who first won office in 1995, is on the November ballot with two little-known candidates. He's widely expected to win re-election in the heavily black, urban and Democratic district that has recently been redistricted to include more rural and white voters.

However, the sporadic and sparse details released about Jackson's condition since his leave began have prompted much scrutiny and speculation. His office did not disclose it publicly until June 25, nearly two weeks after it began. Members of his prominent family -- including his father, the Rev. Jesse Jackson, and wife, Chicago Alderman Sandi Jackson -- have been reluctant to talk.

The timing of the leave -- which comes as Jackson is under a House Ethics Committee investigation for ties to imprisoned former Gov. Rod Blagojevich -- also raised questions. The committee is investigating allegations Jackson was involved in discussions about raising money for Blagojevich's campaign in exchange for the then-governor appointing him to President Barack Obama's vacated U.S. Senate seat.

The announcement of the leave also came just days after a former fundraiser connected to the allegations was arrested on unrelated federal medical fraud charges.

Jackson has repeatedly denied wrongdoing.

The Mayo Clinic's statement went on to detail bipolar disorder and suggested that Jackson's bariatric surgery in 2004 may have played a part in his condition.

"Bipolar II disorder is a treatable condition that affects parts of the brain controlling emotion, thought and drive and is most likely caused by a complex set of genetic and environmental factors," the statement read, adding that his bariatric surgery, specifically a duodenal switch, "is increasingly common in the US and can change how the body absorbs food, liquids, vitamins, nutrients and medications."