3. Twelve-Month Prevalence of Bipolar Disorder by Severity Source: Kessler RC et al. Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry 62:593-602. Total (%) Serious (% of all cases) Moderate (% of all cases) Mild (% of all cases) Bipolar I-II disorders 2.6 82.9 17.1 0.0