Jesse Jackson Jr. says he has "bipolar II depression": What is bipolar II?

In this March 20, 2012 file photo, U.S. Rep. Jesse Jackson Jr., D-Ill., thanks supporters at his primary election night party in Chicago. Jackson has been on medical leave for exhaustion for several weeks and Monday, July 9, 2012, Illinois Sen. Dick Durbin said Jackson has a responsibility to tell the public about his medical condition and his whereabouts. Jackson's staff didn't disclose the fact about the leave right away and then reported July 5 that he was in an inpatient facility battling physical and emotional problems worse than initially thought.
AP Photo/M. Spencer Green
Rep. Jesse Jackson Jr.: Where is he?
In this March 20, 2012 file photo, U.S. Rep. Jesse Jackson Jr., D-Ill., thanks supporters at his primary election night party in Chicago. His family received a statement through the Mayo Clinic on Monday, August 13, 2012, announcing the congressman was being treated for bipolar II depression.
AP Photo/M. Spencer Green

(CBS News) U.S. Congressman Jesse Jackson Jr. is being treated for bipolar II disorder at the Mayo Clinic in Rochester, Minn., the hospital said Monday in a statement.

"Following extensive evaluation, Congressman Jesse Jackson, Jr. is undergoing treatment for Bipolar II depression," the statement read. "Congressman Jackson is responding well to the treatment and regaining his strength."

The congressman had asked the Mayo Clinic to distribute his diagnostic information on his behalf. He's been out of the public eye since a June 10 leave of absence; earlier this month the congressman's office announced he was being treated for depression at the Mayo Clinic.

Bipolar disorder is a mental health condition in which people fluctuate between periods of clinical depression and periods of very good or irritable mood, referred to as mania. These "mood swings" between depression and mania can be very quick.

There are three types of the disorder according to the National Institutes of Health. When people think of the popularized emotional extremes of the disorder, they may be thinking of what used to be called "manic depression" and is now known as bipolar disorder type I. Bipolar type I occurs when a person experiences at least one manic episode and periods of depression.

Bipolar disorder type II on the other hand is in people who never experienced full mania - instead they alternate between depression and periods of high energy and or impulsiveness that are not as extreme as mania, called "hypomania."

Symptoms of hypomanic episodes include flying suddenly from one idea to the next, rapid, pressured loud speech, increased energy with a decreased need for sleep and generally seeming like the "life of the party," WebMD reports. Other signs include making jokes or taking an intense interest in other people and displaying an infectious positive attitude. That however may lead to engaging in impulsive behaviors that may risk a person's health.

A third kind of bipolar disorder is milder and exhibits less severe mood swings, and is called cyclothymia. People who suffer from either bipolar II disorder or cyclothymia may be wrongly diagnosed as having depression, according to the NIH.

In the statement, the Mayo Clinic said bipolar II affects parts of the brain that control for emotion, thought and drive and "is most likely caused by a complex set of genetic and environmental factors."

Having blood relatives with bipolar disorder, being in your early 20's, experiencing periods of high stress, abusing drugs or alcohol and going through a major life change like the death of a loved one may raise risk for developing bipolar disorder, according to the Mayo Clinic's bipolar disorder website.

According to the Clinic, people with bipolar II may have some changes in their functioning but typically can carry on with their normal daily routine. The clinic also said people with bipolar II have periods of depression that typically last longer than periods of hypomania.

Hypomania may not cause unhealthy behavior and as such may go unnoticed or untreated, according to WebMD, whereas mania indicative of bipolar disorder type I may require hospitalization or medications.

Treatment varies by individual, but mood stabilizers such as Lithium, Depakote and Lamictal may be prescribed to prevent consequences of a hypomanic episode, in addition to antipsychotic drugs like Abilify and Risperdal, and benzodiazepines like Xanax, Ativan and Valium.

Antidepressants Seroquel and Seroquel XR are FDA-approved to treat bipolar disorder type II depression, reports WebMD, but other common antidepressants like Prozac, Zoloft and Paxil are sometimes prescribed. Therapy sessions may also be beneficial for people with the disorder.

The clinic's statement also noted that Jackson had previously underwent gastric bypass surgery in 2004, which it said can change how the body absorbs food, liquids, vitamins, nutrients and medications.

The statement was later revised Monday afternoon to say the congressman specifically underwent a duodenal switch, which could lead to those changes in absorption.

In that procedure, a larger portion of the stomach is left intact as would be left from a gastric bypass, including the pyloric valve that regulates draining of contents from the stomach into the small intestine. The duodenum is divided near this valve, and the small intestine is also divided. The lower portion of small intestine is attached to the newly shortened duodenal segment while the remaining duodenal segment is connected to the pancreas and gallbladder, restricting food intake and calorie and nutrient absorption by the small intestine.

Dr. Jaime Ponce, president of the American Society for Metabolic and Bariatric Surgery, told The Associated Press there is no evidence that a duodenal switch can cause bipolar disorder. She said a deficiency of the nutrient thiamine can cause a brain condition that may mimic bipolar disorder, but "bipolar disorder is totally different."