Biology and recent brain imaging studies in affective psychoses.

Psychosis is a cardinal symptom of schizophrenia, but also occurs in other psychiatric conditions, including mood disorders. In many instances, brain abnormalities in psychotic and mood disorders appear to be on a spectrum, with the most marked changes in schizophrenia, followed by psychotic mood disorders, followed by nonpsychotic mood disorders. Such observations are consistent with the notion that mood disorders and schizophrenia represent a continuum of disease. However, in some instances, cerebral changes with psychosis may be qualitatively different, rather than merely more severe than those seen in mood disorders, more consistent with the theory that they are discrete entities. We review brain imaging studies that have advanced our knowledge of psychosis in mood disorders, with respect to the continuum versus discrete entity hypotheses.