PART B: Background Information and Review of Available Evidence

IV. DISEASE DEFINITION, NATURAL HISTORY AND COURSE, AND EPIDEMIOLOGY

A. Definition of Bipolar Disorder

According to DSM-IV-TR (1), patients with bipolar I disorder have had at least one episode of manic (criteria for manic episode are presented in). Some patients have had previous depressive episodes (Table 3), and most patients will have subsequent episodes that can be either manic or depressive. Hypomanic and mixed episodes (and, respectively) can occur, as well as significant subthreshold mood lability between episodes. Patients meeting criteria for bipolar II disorder have a history of major depressive episodes and hypomanic episodes only. Patients may also exhibit significant evidence of mood lability, hypomania, and depressive symptoms but fail to meet duration criteria for bipolar II disorder, thereby leading to a diagnosis of bipolar disorder not otherwise specified. Finally, cyclothymic disorder may be diagnosed in those patients who have never experienced a manic, mixed, or major depressive episode but who experience numerous periods of depressive symptoms and numerous periods of hypomanic symptoms for at least 2 years (1 year in children), with no symptom-free period greater than 2 months. The subtypes of bipolar disorder, as well as selected other affective illnesses, are summarized and compared in Table 6.

In addition to providing definitions of bipolar disorder, DSM-IV-TR also includes specifiers describing the course of recurrent episodes, such as seasonal pattern, longitudinal course (with or without full interepisode recovery), and rapid cycling.

Some investigators have advocated moving from a categorical to a more dimensional perspective in characterizing bipolar disorder. In particular, this perspective includes the concept of a bipolar spectrum that would encompass a range of presentations not currently considered bipolar (149). For example, a patient with antidepressant-induced hypomanic symptoms would be considered to have a form of bipolar disorder under the spectrum conceptualization.

B. Natural History and Course

Bipolar disorder is generally an episodic, lifelong illness with a variable course. The first episode of bipolar disorder may be manic, hypomanic, mixed, and depressive. Men are more likely than women to be initially manic, but both are more likely to have a first episode of depression. Patients with untreated bipolar disorder may have more than 10 total episodes of mania and depression during their lifetime, with the duration of episodes and interepisode periods stabilizing after the fouth or fifth episode (150). Often, 4 years or more may elapse between the first and second episodes, but the intervals between subsequent episodes usually narrow. However, it must be emphasized that variability is the hallmark of this illness. Thus, when taking a history, a number of longitudinal issues must be considered, including the number of prior episodes, the average length and severity of episodes, average interepisode duration, and the interval since the last episode of mania or depression.

Frequently, a patient will experience several episodes of depression before a manic episode occurs (34,151). Consequently, bipolar disorder should always be considered in the differential diagnosis of depression. Patients very often do not report prior episodes of mania and hypomania and instead seek treatment for complaints of depression, delaying correct diagnosis (5,152-157). For a patient who is not educated about bipolar disorder, symptoms of dysphoric hypomania may not be recognized or reported. Therefore, the psychiatrist needs to ask explicity about prior manic or hypomanic episodes, since knowledge of their presence can influence treatment decisions. The psychiatrist should also ask about a family history of mood disorders, including mania and hypomania. Consultation with family members and significant others may be extremely useful in establishing family history and identifying prior affective episodes.

In addition to substance abuse and risk-taking behavior, other cross-sectional features that can have an impact on diagnosis and treatment planning include the presence of psychotic symptoms or cognitive impairment and the risk of suicide or violence to persons or property (41).

Suicide rates are high among bipolar disorder patients. Completed suicide occurs in an estimated 10% - 15% of individuals with bipolar I disorder. Suicide is more likely to occur during a depressive or a mixed episode (8-13). Pharmacotherapy may substantially reduce the risk of suicide (56,60,153). For example, in an 11-year follow-up study of 103 patients with bipolar disorder who were receiving lithium, death rates were well below those expected for this group on the basis of age and sex (154).

Bipolar disorder causes substantial psychosocial morbidity, frequently affecting patients' relationships with spouses or partners, children, and other family members as well as their occupation and other aspects of their lives. Even during periods of euthymia, patients may experience impairments in psychosocial functioning or residual symptoms of depression or mania/hypomania. It is estimated that as many as 60% of people diagnosed with bipolar I disorder experience chronic interpersonal or occupational difficulties and subclinical symptoms between acute episodes (13,33,34,158-164). Divorce rates are substantially higher in patients with bipolar disorder, approaching two to three times the rate of comparison subjects (152). The occupational status of patients with bipolar is twice as likely to deteriorate as that of comparison subjects (152). The occupational status of patients with bipolar disorder is twice as likely to deteriorate as that of comparison subjects. Patients' ability to care or themselves, degree of disability or distress, childbearing status or plans, availability of supports such as family or friends, and resources such as housing and finances also bear on treatment plans.