At present the DSM bipolar diagnoses are those identified above, with all other mood disorders that fall outside the “normal” range considered in the category “not otherwise specified” (NOS). But there is actually a very large range in the presentation of patients within this category, and the present divisions have more to do with diagnostic convenience than a true clinical picture. The richness and complexity of mood disorders is not well captured by the present taxonomy.

13.2.1 Mood Episodes

Major depressive episodes are defined by discrete periods of depressed or “blue” mood or loss of interest or pleasure in life that typically endures for weeks but must last for at least 2 weeks (see Chapter 14). These symptoms are often accompanied by an increase or decrease in sleep or appetite, decreased energy, and impaired cognition. Depressive episodes in manic–depressive disorder are indistinguishable from those in major depressive disorder. About 75% of people with manic–depressive disorder experience depressive episodes characterized by decreased sleep and appetite, while about 25% experience more “atypical” symptoms of increased sleep and appetite, rates that are indistinguishable from those in unipolar depression. Thus with regard to depressive episodes, the differential diagnosis between major depressive and manic–depressive disorders is made by longitudinal course not by cross-sectional symptom analysis.

Manic episodes are defined by discrete periods of abnormally elevated, expansive, or irritable mood accompanied by marked impairment in judgment and social and occupational function. These symptoms are frequently accompanied by unrealistic grandiosity, excess energy, and increases in goal-directed activity that frequently have a high potential for damaging consequences. Hypomanic and manic symptoms may be identical, but hypomanic episodes are less severe. A person is “promoted” from hypomania to mania (type II to type I) by the presence of one of three features: psychosis during the episode, sufficient severity to warrant hospitalization, or marked social or occupational role impairment. This is an imperfect set of criteria, however, because the phenomenologic differentiation between hypomania and mania is not always straightforward.

The DSM divides bipolar disorders into two types, “bipolar I” and “bipolar II.”

13.2.2 Bipolar I disorder

Bipolar I disorder is characterized by one or more manic episodes, usually alternating with major depressive episodes. During the manic episode the patient may exhibit inflated self-esteem or grandiosity, decreased need for sleep, being more talkative than usual, flight of ideas, distractibility, increase in goal-oriented activity, and excessive involvement in risky activities.

The symptoms are severe enough to disrupt the patient’s ability to work and socialize, and may require hospitalization to prevent harm to self or others. Manic episodes usually begin suddenly and last from a few days to a few months.

13.2.3 Bipolar II disorder

Bipolar II disorder is characterized by the patient having had a major depressive episode (either current or past) and at least one hypomanic episode over at least 4 days. Most hypomanic episodes in bipolar II disorder occur immediately before or after a major depressive episode. Bipolar II disorder differs from bipolar I in that the patient has never had a manic or mixed episode. Bipolar II patients may have had an episode in which they experienced a persistently elevated, expansive, or irritable mood (hypomania) that is clearly different from their usual mood. With Bipolar II, however, the patient does not experience hypomanic symptoms severe enough to cause marked social or occupational dysfunction or to require hospitalization. Bipolar II disorder can present diagnostic challenges, particularly if the patient presents for the first time with a depressive episode.

13.2.4 Cyclothymic Disorder

Cyclothymia is a disorder resembling bipolar disorder, with less severe symptoms. Cyclothymic disorder presents as a “subclinical” bipolar I disorder. Patients with cyclothymic disorder experience repeated periods of non-psychotic depression and hypomania for at least 2 years (1 year for children and adolescents). The opposing manifestations of depression and hypomania are seen in the following pairs of symptoms: feelings of inadequacy (during depressed periods) and inflated self-esteem (during manic periods); social withdrawal and uninhibited social interaction; sleeping too much and too little; and diminished and increased productivity at work. Cyclothymic disorder is diagnosed only if a major depressive or manic episode has never been present.

13.2.5 Bipolar Depression

At present, the DSM-IV criteria for major unipolar depression substitute for a genuine bipolar depression diagnosis. On the surface, there is little to distinguish between bipolar and unipolar depression, but certain “atypical” features may exist. People with bipolar depression are more likely to have psychotic features and more classic “slowed down” symptoms such as hypersomnia or fatigue, while those with unipolar depression are more prone to crying spells and significant anxiety (with difficulty falling asleep). Because bipolar II patients spend far more time depressed than hypomanic (50% depressed versus 1% hypomanic, according to a 2002 NIMH study) misdiagnosis is common. The implications for treatment are enormous insofar as misdiagnosis can result in inappropriate medication, which may confer no benefit, but which can drastically worsen the outcome of the illness, including switches into mania or hypomania and cycle acceleration. Bipolar depression calls for a far more sophisticated medications approach, which makes it absolutely essential that those with bipolar II be properly diagnosed.

13.2.6 Additional Features: Psychosis and Rapid Cycling

Psychosis is an episode modifier and can occur in either depression or mania. If psychotic symptoms are limited to the major mood episode, the individual is considered to have manic–depressive disorder with psychotic features. On the other hand, if psychotic symptoms endure significantly into periods of normal mood, the diagnosis of schizoaffective disorder is made.