Expanding the group of bipolar disorders.

The concept of bipolar disorder is an ongoing process. Its roots can be found in the work of the ancient Greek physician Aretaeus of Cappadocia, who assumed that melancholia and mania are two forms of one and the same disease; he actually believed that mania was a more severe form of melancholia. Falret [Bull. Acad. Natl. Med., Paris (1851)] and Baillarger [Ann. Méd-psychol. 6 (1854) 369] from France are the fathers of the modern understanding of bipolar disorders. But the definitive distinction of bipolar from unipolar disorders occurred in 1966 by Jules Angst and Carlo Perris in Europe, and later supported by Winokur and colleagues in the United States. Schizoaffective disorders should also be dichotomized into unipolar and bipolar forms. Another extension of the group of bipolar disorders is the contemporaneous rebirth of cyclothymia, originally described in the work of Kahlbaum (1882) and Hecker (1898) [Z. Prakt. Arzte 7 (1898) 6]; the main importance of cyclothymia today is its relevance for what Akiskal [Clin. Neuropharm. 15(1) (1992) 632] considers the realm of the 'soft bipolar spectrum.' A further interesting development is the renewed research in the field of 'mixed states' which originated in the classic Handbook of Kraepelin a century ago (1899).