Updated 07/05/12 – 3:52 p.m.

CHICAGO (CBS) – Congressman Jesse Jackson Jr.’s office said the medical condition that has forced him to take a leave of absence is more serious than originally believed, and he will require extended medical treatment.

Last week, Jackson’s office announced he had been on medical leave since June 10, due to “exhaustion,” but according to a statement from his spokesman Frank Watkins, “Congressman Jackson’s medical condition is more serious than we thought and initially believed.”

“Recently, we have been made aware that he has grappled with certain physical and emotional ailments privately for a long period of time,” Watkins added.

The congressman is being treated at an undisclosed “in-patient medical facility” and his doctors have said he “will need to receive extended in-patient treatment, as well as continuing medical treatment thereafter.”

The statement did not provide any further details about the specific ailments that Jackson is suffering from, or how long his medical leave will last.

“We ask that you keep Congressman Jackson and his family in your thoughts and prayers during this difficult period,” Watkins wrote.

House Minority Leader Nancy Pelosi’s press office said they were unaware of Jackson’s disclosure that he was receiving in-patient treatment for emotional and physical ailments, as of Thursday afternoon.

Jackson has missed dozens of votes on Capitol Hill recently.

Jackson has been under enormous pressure in recent years: his name has been linked to the U.S. Senate seat scandal that took down former Gov. Rod Blagojevich, he’s facing a House Ethics Committee investigation, he has been dealing with marital problems over his affair with a restaurant hostess, and a key Jackson fundraiser was indicted last month, just days before Jackson’s office disclosed he was on leave.

That fundraiser, Raghuveer Nayak, was a key figure in the Senate seat scandal, and is also at the center of the Ethics Committee probe. Nayak allegedly offered to raise up to $6 million in campaign cash for Blagojevich to appoint Jackson to President Barack Obama’s old Senate seat. Jackson has denied directing Nayak to offer campaign cash for the seat, or any knowledge of such a deal.

Jackson’s chief of staff, Rick Bryant, has insisted Nayak’s arrest on racketeering, fraud, and tax evasion charges was not connected to Jackson’s leave of absence. He said the congressman had planned an announcement earlier, but delayed it after news of Nayak’s arrest.