Psychopathology of stable and unstable mixed states: a historical view

The concept of mixed states was proposed at the end of last century by Kraepelin and Weygandt to confer unity to manic-depressive illness and to better differentiate this disease from dementia praecox. The concept has been further elaborated by the Hamburg and Vienna schools (Mentzos and Berner, respectively), and dichotomized in stable and unstable mixed states. Stable mixed states represent a condition of the synchronic copresence of symptoms of both polarities; unstable mixed states, or "mixed pictures," are characterized by the rapid cycling of these symptoms. The former represent clinical expressions of bipolar disorder, and the latter represent trans-nosological conditions with multiple outcomes. Current North American nosology retains the original Kraepelinian concept of stable mixed states and ignores the concept of unstable mixed states, which is very close to the concept of ultradian cycling proposed by Kramlinger and Post in 1996.