Classification of bipolar disorders-implications for clinical research

The classification of mood disorders has been a subject of scientific debate for more than 2500 years (1,2), and a precise delineation of these illnesses and its various clinical manifestations has yet to emerge. Many aspects of this discussion have recently been reviewed by Akiskal (2) and supplemented by commentaries from authoritative researchers. In this chapter we will give an overview of the current classification, the boundaries of bipolar disorder with other major psychiatric illnesses, the validity and reliability of diagnosis, and the implications for neuropsychiatric research. As all classifications that are based on clinical description rather than on etiology and pathophysiology are deemed to be temporary, we will begin with a brief historical overview and end with some areas that need further clarification.