In this occasional feature, members of the Psych Congress Steering Committee and faculty answer questions asked by attendees at Psych Congress meetings.
QUESTION: What criteria differentiates between bipolar disorder with psychotic features and the bipolar type of schizoaffective disorder?
ANSWER: Technically, the Diagnostic and Statistical Manual of Mental Disorders (DSM)-based definition would differentiate a bipolar disorder episode with psychotic features from schizoaffective disorder, bipolar type based on persistence of psychotic features outside of a distinctive mood episode.
Although a DSM committee has gone to great pains to create a clear distinction between these two diagnostic categories, Mother Nature is refusing to fully cooperate. Longitudinal studies have provided evidence of “diagnostic instability.” Namely, a single individual may undergo a conversion, whereby a condition which initially satisfied the criteria for bipolar disorder eventually “converts” to schizoaffective disorder.
Furthermore, large scale genome-wide association studies (GWAS) have suggested that there is a significant genetic overlap between bipolar spectrum and schizophrenia. If one counts each schizophrenia “vulnerability” gene towards a polygenic score, we find that individuals who meet diagnostic criteria for bipolar disorder but have a higher schizophrenia polygenic score may be much more likely to experience mood-incongruent delusions and to manifest a substantially reduced likelihood of lithium response.
In summary, although bipolar disorder, schizoaffective disorder, and schizophrenia are currently treated as distinctive diagnostic entities, they may be just different points on a biological/genetic continuum, linked by significant “gray zones” of overlap.
—Psych Congress Steering Committee member Vladimir Maletic, MD, MS,Clinical Professor of Psychiatry and Behavioral Science, University of South Carolina School of Medicine, Greenville
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