Psychotic bipolar disorders: dimensionally similar to or categorically different from schizophrenia?

For over a century, clinicians have struggled with how to conceptualize the primary psychoses, which include psychotic mood disorders and schizophrenia. Indeed, the nature of the relationship between mood disorders and schizophrenia is an area of ongoing controversy. Psychotic bipolar disorders have characteristics such as phenomenology, biology, therapeutic response, and brain imaging findings, suggesting both commonalities with and dissociations from schizophrenia. Taken together, these characteristics are in some instances most consistent with a dimensional view, with psychotic bipolar disorders being intermediate between non-psychotic bipolar disorders and schizophrenia spectrum disorders. However, in other instances, a categorical approach appears useful. Although more research is clearly necessary to address the dimensional versus categorical controversy, it is feasible that at least in the interim, a mixed dimensional/categorical approach could provide additional insights into pathophysiology and management options, which would not be available utilizing only one of these models.