CHICAGO — 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.

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.

Bipolar II is a treatable condition that affects parts of the brain controlling emotion, thought and drive and is likely caused “by a complex set of genetic and environmental factors,” the clinic said. The statement also mentioned that Jackson underwent weight loss surgery in 2004 and said such a surgery can change how the body absorbs foods and medications, among other things.

His father, the Rev. Jesse Jackson, wouldn’t say much about the diagnosis.

“I’m glad he’s getting the treatment he needs and is responding well,” the elder Jackson said, adding that “there’s no timetable” for his recovery.

Experts and mental health advocates say many people are able to work and function in their daily lives while managing treatment.