Bipolar disorders are diagnosed using the criteria for both manic and major depressive episodes. In this category of major affective disorder, both the affective poles of mania and depression are present. Bipolar disorders are diagnosed as bipolar disorder, manic, if the current episode meets criteria for a manic episode and as bipolar disorder, depressed, if the episode meets criteria for a major depressive episode. Bipolar patients who have more rapid cycling, with manic and depressive episodes alternating every few days or weeks, are classified as bipolar disorder, mixed. Bipolar depression is more frequent in women than men in a ratio ranging from 1.2:1 to 2:1. Men have significantly more manic than depressive episodes, whereas women have significantly more depressive than manic episodes. The age of risk for bipolar disorder extends from as early as 6 or 7 years to over 65, but the peak age of onset in both men and women for the first attack is in the early thirties, with a mean age of onset of 32.5 years. About two-thirds of first episodes are manic and 60 percent of these patients will have a predominantly manic course, while the remaining 25 to 30 percent manifest primarily depressive episodes. Most natural-course studies of untreated bipolar patients generally agree that they will average nine diagnosable affective episodes during their lifetimes (range 1 to more than 20). The pattern is that the cycle length, which is measured from the onset of one episode to the onset of the next, will decrease and the number of episodes will increase over time. For example, in untreated bipolar patients the time between the first and second episode averages from 3.5 to 4 years, between the second and third episodes about 2 years, and between episodes three and four somewhere between 12 and 18 months. Episode duration is from 4 to 13 months, and the average is about 8.5 months. Attempts have been made to categorize affective episodes in the bipolar patient based on how often the episodes occur in juxtaposition to those of opposite polarity. The vast majority of episodes are uniphasic, i.e., a manic or depressive episode is preceded by a symptom-free period; however, approximately 10 or 15 percent are biphasic with a depressive episode more often preceding the manic.
There is a small but distinct group of bipolar patients who manifest very rapid cycling patterns (bipolar disorder, mixed). The rapid cycler is a patient who presents with more than four or five episodes in 1 year, but there are patients who have considerably more episodes and there are case reports of patients cycling every 24 h. The rapid-cycling bipolar patient has eight times the number of affective episodes in his or her lifetime in comparison to slow cyclers. Eighty percent of rapid cyclers are women, and the appearance of rapid cycling is sometimes related to impaired thyroid function. Although it is still controversial, there is evidence that rapid cycling may be induced by a course of tricyclic antidepressants and can only be effectively controlled after the patient is euthyroid and removed from tricyclics.
The life-long intensity of illness in bipolar disorder, even among the slow cyclers, is much more extreme than it is in unipolar disorder. Bipolar patients have significantly more episodes of illness, more hospitalizations, and spend more total time in the hospital during their lifetimes.