There are no reports of differential incidence of Bipolar I Disorder based on race or ethnicity. There is some evidence that clinicians may have a tendency to overdiagnose Schizophrenia (instead of Bipolar Disorder) in some ethnic groups and in younger individuals.
Approximately 10%-15% of adolescents with recurrent Major Depressive Episodes will go on to develop Bipolar I Disorder. Mixed Episodes appear to be more likely in adolescents and young adults than in older adults.
Recent epidemiological studies in the United States indicate that Bipolar I Disorder is approximately equally common in men and women (unlike Major Depressive Disorder, which is more common in women). Gender appears to be related to the number and type of Manic and Major Depressive Episodes. The first episode in males is more likely to be a Manic Episode. The first episode in females is more likely to be a Major Depressive Episode. In men the number of Manic Episodes equals or exceeds the number of Major Depressive Episodes, whereas in women Major Depressive Episodes predominate. In addition, Rapid Cycling is more common in women than in men. Some evidence suggests that mixed or depressive symptoms during Manic Episodes may be more common in women as well, although not all studies are in agreement. Thus, women may be at particular risk for depressive or intermixed mood symptoms.
Women with Bipolar I Disorder have an increased risk of developing subsequent episodes in the immediate postpartum period. Some women have their first episode during the postpartum period. The specifier With Postpartum Onset may be used to indicate that the onset of the episode is within 4 weeks of delivery. The premenstrual period may be associated with worsening of an ongoing Major Depressive, Manic, Mixed, or Hypomanic Episode.