Rep. Jackson Missing: A Look at Mood Disorders

(CHICAGO) -- The medical condition keeping Rep. Jesse Jackson Jr. out of Congress for the past month was finally revealed and not revealed at the same time: a mood disorder, a condition that can be anything from major depression to bipolar disorder.

Although a mood disorder can be many different things, the most common form is depression, and doctors say such a disorder has to be severe for a patient to be admitted to an inpatient treatment facility. Most people admitted are either suffering from delusions or are suicidal.

One senior aide to Jackson spoke to ABC News and denied that the congressman had attempted suicide.

Mood disorders are fairly common in the United States. Almost 7 percent of U.S. adults have depression in a given year, and almost 17 percent of Americans will experience it in their lifetime, according to the National Institutes of Mental Health.

The numbers are slightly lower for bipolar disorder: Nearly 4 percent of Americans will have it in their life. Mood disorders like these have a variety of physical and environmental triggers.

Jackson's office told ABC News on Thursday that the congressman has been in a treatment facility for a few weeks, but would not speculate on how long he would be there.

Copyright 2012 ABC News Radio