Illinois Democratic Rep. Jesse Jackson Jr. is undergoing treatment for bipolar II depression, according to a statement issued this afternoon from the Mayo Clinic.

“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 clinic wrote.

In this Oct. 16, 2011 file photo, Rep. Jesse Jackson, Jr., D-Ill., is seen during the dedication of the Martin Luther King Jr. Memorial in Washington. (Charles Dharapak/AP)

In early August Sandy   Jackson, the Congressman’s wife, said that “they are now trying to find out if his depression, which has not yet been diagnosed as a bipolar disorder, is connected to the weight-loss surgery. We don’t know.”

Jackson underwent bariatric surgery in 2004 — a procedure known as a duodenal switch — in 2004. His wife said last week that doctors were looking into a possible connection between the procedure and his current condition. “I never really wanted him to have the gastric surgery in the first place,” she told the Chicago Sun-Times.

Bipolar disorder is characterized by swings between mania and depression. According to the clinic, bipolar II is less severe than bipolar I; mania is less severe, while periods of depression last longer.

Jackson Jr. won a contested primary against former Rep. Debbie Halvorson earlier this year and is expected to coast to a ninth term in November.