What Are the Different Types of Bipolar Disorder?

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Bipolar I Disorder

People with Bipolar I disorder have full-blown manic attacks and deep, paralyzing depressions. A World Health Organization survey found the prevalence rate of bipolar I disorder to be 0.6 percent. Bipolar I disorder usually starts in late adolescence or early adulthood, with the peak onset during the third decade of life (ages 20 through 29.)

Bipolar I is often a relapsing and remitting illness, meaning that its symptoms come and go. This feature of bipolar I—it is a feature of all mood disorders—makes it challenging to diagnose, challenging to treat, and fiendishly difficult to study.

Bipolar I: What to Expect

Many excellent clinical studies about bipolar disorder were done in the years before effective treatments were available. How many episodes of illness did patients have in the days before treatment was available? How long did their episodes last? What was the length of time between episodes?

In a 1942 study, researchers looked at the medical records of 66 patients with “manic-depressive psychosis.” A few patients had only one episode of illness in the study period. About one-third had 2 to 3 episodes, about one-third had 4 to 6 episodes, and about one-third had more than 7. A few had 20 or more episodes. Unfortunately, there is no way to know whether the individual will have another 2 or 3 episodes during his lifetime or more than 20.

Subsequent studies have shown that, if untreated, episodes of bipolar disorder often occur more frequently as patients age, and episodes seemed to be triggered more easily.

Many patients with bipolar I disorder have nearly complete remission of their symptoms between episodes. This illness pattern often predicts that an individual will have an excellent response to treatment with lithium.

Bipolar II Disorder

People with bipolar II disorder have fully developed depressive episodes and episodes of hypomania. These patients never develop full-blown mania, although they often have mild mixed states.

The World Health Organization estimates that the lifetime prevalence of bipolar II disorder is 0.4 percent.

Initially, some researchers suspected that patients with a history of hypomania and depression but not mania were in the early stages of “manic-depression.” But several observational studies in the 1970s and 80s showed that this was not the case. One of these, written by Dr. William Coryell and his colleagues, followed patients with recurrent depressions and hypomania for some years and found that fewer than 5 percent of them ever became manic. Bipolar II is not merely a prelude to “full-blown” manic-depressive illness; bipolar II patients are not in the early stages of bipolar I.

Bipolar II: What to Expect

Bipolar II is sometimes erroneously referred to as a milder form of bipolar I. But although patients with bipolar II do not develop the most severe symptoms of full-blown mania, they tend to have symptoms more of the time. Long periods of depression are typical of bipolar II disorder and can be even more debilitating than the dramatic but shorter-lived episodes of bipolar I illness.

Persons with bipolar II are more likely to have a seasonal variation in their symptoms, meaning that they tend to get depressed in the fall and winter and feel better—or even develop hypomania—in the spring and summer. Whereas patients with bipolar I frequently have irritable manic symptoms, the hypomanic periods of bipolar II patients are characterized by an elated mood.

Concerning depressive symptoms, patients with bipolar II disorder more often suffer from psychomotor agitation, guilty feelings, and thoughts of suicide. Bipolar II patients also have a higher incidence of phobias and eating disorders. Typically, hypomanic episodes taper off as the bipolar II patient ages. When they reach middle age, depression is usually the predominant mood.

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Cyclothymic Disorder

People with cyclothymic disorder have frequent short periods of depressive symptoms and hypomania separated by only brief periods of normal mood. By definition, the patient does not have either fully developed major depressive episodes or fully developed manic episodes. These patients essentially cycle almost continuously between mild depression and mild elation.

Modern studies on community populations have come up with an estimate of between 0.4 and 2.4 percent.

Cyclothymia is now considered a subtype of bipolar disorder, a classification supported by family-history studies. Patients with cyclothymia often have relatives with bipolar disorder but rarely have relatives suffering from depression only. Treatment experiences seem to confirm this relationship: The mood swings of cyclothymic disorder often respond to many of the same treatment approaches as other bipolar disorders.

Cyclothymic Disorder: What to Expect

Individuals with cyclothymic disorder have frequent ups and downs of mood, with only comparatively few periods of “normal” mood.

Cyclothymic disorder tends to begin very early in life. A study of 894 young patients (aged 5 to 17 years) found that nearly three-quarters of the patients with cyclothymic disorder had first experienced symptoms before age ten.

"Soft" Bipolar Disorders

“Soft” bipolar disorders are mood disorders with some features of bipolar disorder, but that doesn’t fit the pattern of better-defined subtypes.

For about a half-century, psychiatry divided mood disorders into cases of unipolar depression, an illness characterized by only depressive symptoms, and bipolar disorders, in which patients suffer depressive episodes but also manic, hypomanic, or mixed states.

“Soft” bipolar disorders seem to challenge this way of thinking; many of these patients have an illness dominated by depressive symptoms with only the slightest colorings of mania. Sometimes, a family history of bipolar disorder is the only hint. More frequently, they have brief periods of elevated mood that they don’t feel are particularly abnormal but that, when examined more closely, bear the hallmarks of hypomania: the decreased need for sleep, increased energy, uncharacteristic overconfidence, and loss of inhibitions. They can have periods of agitation and irritability that last only a few hours and possibly represent mild mixed states.