February 13, 2020
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Five new subgroups may change psychosis taxonomy

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Dominic B. Dwyer

Researchers have identified psychosis subgroups that may inform ongoing efforts to redefine psychosis taxonomy using updated criteria, according to results of a longitudinal cohort study published in JAMA Psychiatry.

“This study shows that we can use computers to help us to rethink how people with psychosis symptoms are diagnosed,” Dominic B. Dwyer, PhD, of the department of psychiatry and psychotherapy at Ludwig Maximilian University of Munich, told Healio Psychiatry. “This is clinically important because it may lead to the definition of more specific psychosis categories that increase the precision of psychiatric care and research.”

According to Dwyer and colleagues, schizophrenia and bipolar diagnoses classify patients according to shared patterns of psychiatric history, illness courses and symptoms. Despite evidence of overlapping genetic risk profiles, symptomatic ambiguity and heterogeneous illness courses, these categories drive clinical practice and research. As a result, researchers have questioned the existing taxonomy, with new psychosis configurations currently under consideration.

In the present study, the researchers used data-driven methods to detect psychosis subgroups and examine their illness courses over 1.5 years, as well as polygenic scores for major depression disorder, bipolar disorder, schizophrenia and educational achievement. They conducted the study across 18 sites and collected data from a referred sample of 1,223 individuals with DSM-IV diagnoses of brief psychotic disorder, bipolar affective disorders 1 and 2, schizophreniform disorder, schizoaffective disorder and schizophrenia. The researchers constructed a clinical battery of 188 variables that measured clinical history, demographic characteristics, cognition, functioning and symptoms.

In the discovery sample, they included 765 individuals, of which 341 (44.6%) were women, and the mean age was 42.7 years. They found and labelled five subgroups — high-functioning psychosis (n = 252), affective psychosis (n = 252), depressive psychosis (n = 131), severe psychosis (n = 86) and suicidal psychosis (n = 44). Further, Dwyer and colleagues found illness courses with significant quadratic interaction terms for psychosis symptoms, depression symptoms, global functioning and quality of life. They noted that the depressive and severe psychosis subgroups exhibited the lowest functioning and quadratic illness courses with partial recovery followed by reoccurrence of severe illness. They also found differences for educational attainment polygenic scores but not for diagnostic polygenic risk. In a validation cohort, they largely replicated these results.

“I was very interested when I saw the findings because they showed me a different way to think about individuals who had been suffering from psychosis for many years,” Dwyer said. “When we re-categorized people, it was exciting to see that this helped us to detect hidden illness trajectories and genetic associations.” – by Joe Gramigna

Disclosures: Dwyer reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.