| Prevalence |
Between 0.4% and 1.6% of Americans suffer from bipolar I disorder; worldwide the prevalence is 0.6% (Merikangas et al., 2011). Approximately 0.5–1% of Americans will develop bipolar II disorder in their lifetimes (Merikangas et al., 2007); worldwide the prevalence is 0.4% (Merikangas et al., 2011). |
| Onset |
Both men and women begin to have symptoms of bipolar I and II disorder by age 20, on average, although the symptoms do not necessarily include full-blown manic attacks. |
| Comorbidity |
Up to 75% of those with any bipolar disorder are also diagnosed with another mental disorder, such as anxiety disorders and eating disorders (Merikangas et al., 2011). |
| Course |
People who have had one manic episode have a 90% chance of having at least one further manic episode. Bipolar II disorder typically has a more chronic, though less severe, course than bipolar I disorder (Judd et al., 2003). People with either type of bipolar disorder have MDEs that are more severe and lead to more lost work days than do people with depressive disorders (Kessler, Akiskal, et al., 2006). Between 5 and 15% of people with bipolar II will have a manic episode at some point, thereby changing the diagnosis to bipolar I. |
| Gender Differences |
Bipolar I disorder is equally common among males and females; research indicates that bipolar II disorder may be more common among females than among males. Almost half of men with bipolar I disorder have their first full-blown manic episode by age 25; in contrast, only one third of women have their first manic episode by that age (Kennedy et al., 2005). In males, the number of manic episodes (or hypomanic, in the case of bipolar II disorder) often equals or exceeds the number of MDEs, whereas in women, MDEs predominate (Altshuler et al., 2010). For women, having a bipolar disorder boosts the risk of developing mood episodes (of any kind) immediately after giving birth; women are also more likely to have rapid mood cycling. |
| Cultural Differences |
In one international study, the United States has the highest rate of bipolar disorders, with up to 4.4% of Americans having the disorder in their lifetimes (Merikangas et al., 2011). |
| Source: Unless otherwise noted, the source for information is American Psychiatric Association, 2013. |