CHICAGO – Jesse Jackson Jr.'s transfer to the Mayo Clinic in Minnesota could indicate a complicating physical illness arose during the Illinois congressman's treatment for depression, several experts in psychiatric care said Saturday.

The Chicago Democrat has been on a secretive leave of absence for nearly seven weeks, during which his office has released only occasional snippets of information, including that he was undergoing treatment for a "mood disorder" at an undisclosed location.

On Friday, the Mayo Clinic distributed a statement from the congressman that said he had been transferred there for "extensive inpatient evaluation for depression and gastrointestinal issues." The clinic would not release more information Saturday.