It used to be called manic depression, an oxymoron if ever there was one. Today the condition is classified as bipolar disorder, which better describes the brain disorder that causes dramatic shifts in mood, energy, activity levels and the ability to carry out daily tasks. Although depression is common on its own, mania is rarely a singular condition. “The two are almost inevitably linked,” says Dr. Ellen Frank, professor emeritus of psychiatry at the University of Pittsburgh. “I have seen a handful of patients, maybe three or four, who claimed they had never been depressed, but they didn’t recognize the depressive episodes.”

[See: Am I Just Sad — or Actually Depressed?]

According the National Institute of Mental Health, or NIMH, bipolar disorder causes “clear changes in mood, energy and activity levels.” These may range from manic episodes of being extremely “up,” elated and energized to depressive periods with very sad, “down” or hopeless feelings. There are four general categories of bipolar disorder:

— Bipolar I is defined by manic episodes that last at least seven days or by manic symptoms that are so severe the patient needs immediate hospital care. Usually, depressive episodes lasting at least two weeks also occur.

— Bipolar II is a pattern of depressive episodes and hypomanic, or milder manic, episodes, not full-blown mania as in bipolar I disorder. “Hypomania doesn’t lead to real problems in relationships or performance,” Frank explains. “The dividing line [between mania and hypomania] is how much trouble the symptoms create. They can lead to promiscuity, altercations, arrests and in extreme forms, mania can include psychosis and delusions. Individuals may believe they have extraordinary powers, they can fly, they are John Lennon, and you don’t see that in hypomania.”

— Cyclothymic disorder, also called cyclothymia, is characterized by numerous periods of hypomanic and depressive symptoms lasting for at least two years in adults and one year in children and adolescents. The difference here is that the symptoms are not severe enough to meet the diagnostic requirements for a hypomanic and a depressive episode.

— Other specified and unspecified bipolar and related disorders are defined by bipolar disorder symptoms that do not match the other three categories.

Bipolar disorder affects men and women equally and can develop at any point in life, but the average age of onset is 25, according to the National Alliance on Mental Illness. Every year, 2.9 percent of the U.S. population is diagnosed with bipolar disorder, and about 83 percent of those cases are classified as severe.

Bipolar disorder is much harder to treat than depression alone, Frank says. “The reality is we have excellent treatments for mania that work quickly, but no great treatment for depression in bipolar disorder. Most of the medications used in depression are capable of provoking mania, so we have to be extremely careful in our use of medications. You want to help patients out of their depression but not risk precipitating mania.”

[See: How to Find the Best Mental Health Professional for You.]

Causes and Risk Factors

The NIMH says most scientists believe there is no single cause for bipolar disorder. It’s more likely that several factors contribute to increased risk, including brain structure and functioning, family history of the disorder and genetics. However, the genetic link is not definite, as studies of identical twins have found that one may develop bipolar disorder while the other may not, and that most people with a family history do not get it themselves.

Creativity and bipolar disorder have also been linked, says David J. Miklowitz, professor of psychiatry and director of the Integrative Study Center in Mood Disorders at UCLA’s Semel Institute for Neuroscience and Human Behavior. “People with bipolar disorder often have very creative people in their family as well as being creative themselves,” he says. “But it is not by any means a 1-to-1 relationship.”

Developing depression as a child may also increase the risk for bipolar disorder later in life. “It appears that childhood depression often switches to bipolar disorder later in childhood, and this switch rate is more common in children than in adults,” says Dr. Janet Wozniak, director of the Pediatric Bipolar Disorder Clinical and Research Program at Massachusetts General Hospital and an associate professor of psychiatry at Harvard Medical School. “Studies show that by the time children reach age 18, 50 percent of depressed patients had signs of bipolar disorder earlier. When you diagnose depression, you need to be mindful of past symptoms of mania.”

Diagnosing bipolar disorder can be tricky, the NIMH says. Patients are more likely to see a doctor when they are depressed than when they are manic, and bipolar disorder may be mistakenly diagnosed as major depression. In addition, some bipolar disorder symptoms are similar to other illnesses, and many people with the disorder also have another mental or behavioral illness, such as anxiety disorder, substance abuse or an eating disorder. They are also at higher risk for thyroid disease, migraine headaches, heart disease, diabetes, obesity and other physical illnesses.

[See: 6 Ways Obesity Can Weigh on the Brain.]

Treatments Can Help

Though treating bipolar disorder is challenging, many people can be helped to control their symptoms. Once diagnosed, treatment usually includes a combination of medication and psychotherapy. Sleep medications may also be used during manic periods. Patients with severe bipolar disorder who are not helped by other means may find relief through electroconvulsive therapy, or ECT.

Bipolar disorder is a lifelong illness, according to the NIMH, and patients need long-term, continuous mental health treatment. That may take some work to find the right combination of therapies, Frank says. “We used to worry in bipolar disorder about the mania and ignore the depression. We have learned in the past decade that, actually, the depressive episodes are much more impairing because they can go on for so long,” she says. “We have come to understand the need to put more energy into finding effective treatments for the depressive side of bipolar disorder.”

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Bipolar Disorder: How Does It Relate to Depression? originally appeared on usnews.com