Mixed States: Historical Impact and Evolution of the Concept

Mixed states have been discussed for more than 2 millennia. The theoretic conception of the coexistence of presumably opposite symptoms of mood or of different psychic domains is well established, although obscured by the presumed separation between bipolar and depressive disorders. Moreover, the lack of response to treatments and severe psychopathology raise important issues requiring urgent solution. The aim of this article was to review the development of the concept of mixed states from the classic literature to modern nosologic systems and to claim for the need of a new paradigm to address the still-open issues about mixed states.