Differentiating between Bipolar Disorder types I and II: results from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC).

OBJECTIVE: Bipolar Disorder I (BD I) and Bipolar Disorder II (BD II) vary considerably, with differences in symptomatology, management and prognosis. For patients with depression, the distinction between BD I and BD II is not always apparent, and hinges on the differentiation between manic/mixed and hypomanic episodes. Other putative differences between patients with BD I and II exist and may assist in distinguishing between these two conditions.

METHODS: Data were obtained from the National Epidemiological Survey on Alcohol and Related Conditions. A total of 1429 subjects were included in our analysis based on DSM-IV criteria, 935 with BD I and 494 with BD II. We examined for differences in a number of variables including demographics, clinical features, depressive symptoms, and co-morbid conditions using t-tests and chi-square analyses for a comparison of means as well as a logistic regression for variables found to be significant.

RESULTS: Key differences between BD I and BD II were identified in all categories in our comparison of means. In the regression analysis, a number of variables were determined to be predictors of BD I, including unemployment (OR=0.6), taking medications for depression (OR=1.7), a history of a suicide attempt (OR=1.8), depressive symptoms such as weight gain (OR=1.7), fidgeting (OR=1.5), feelings of worthlessness (OR=1.6) and difficulties with responsibilities (OR=2.2), as well as the presence of specific phobias (OR=1.8) and Cluster C traits (OR=1.4).

CONCLUSIONS: Our results indicate that in addition to the differences between manic/mixed and hypomanic episodes, other significant differences exist that may be used to help differentiate BD I from BD II.