Rep. Jesse Jackson Jr. Being Treated for Bipolar Disorder

Medical leave finally explained.

U.S. Rep. Jesse Jackson Jr., a Chicago Democrat who took a hushed medical leave two months ago, is being treated for bipolar disorder, the Mayo Clinic announced Monday.

The Rochester, Minn.-based clinic specified his condition as Bipolar II, which is defined as periodic episodes of depression and hypomania, a less serious form of mania.

"Congressman Jackson is responding well to the treatment and regaining his strength," the clinic said in a statement.