Bipolar I - Biploar II distinction

Previous studies, performed in the second half of the last centruy, focused primarily on the two extreme manifestations of major mood disorders (i.e., unipolar major depression and “classical” Bipolar I disorder), and found marked differences in almost all clinical features and diagnostic validators, virtually supporting the strict categorical distinction between unipolar major depressive disorder and bipolar disorder. However, a number of recent studies clearly support the original “unitary” concept of Emil Kraepelin on the continuity between unipolar depression and (bipolar) manic-depressive illness. Nowdays it is well accepted that Bipolar I (depression with a history of mania) and Bipolar II (depression with a history of hypomania but not with mania) disorders represent two prominent clinical phenotypes at the “bipolar edge” of the full unipolar-bipolar spectrum with several similarities and differences. Phenomenologically, Bipolar II disorder is more close to Bipolar I disorder than to unipolar depression.

The clinically most important differences between Bipolar I and Bipolar II disorders are: 1/ Epidemiology, including gender ratio and age of onset, 2/ Genetical (biological) background, 3/Cross-sectional clinical picture of depression, including mixed depression/agitation and psychotic features, 4/ Psychiatric and medical comorbidity, 5/Long-term course and outcome, including rapid cycling and seasonality, 6/ Suicidal behaviour, including both attempted and comleted suicide, 7/ Affective temperament, and 8/ Artistic creativity/criminality.