Probing the boundaries of the Kraepelinian dichotomy: Evidence for a transdiagnostic psychosis phenotype encompassing subclinical and clinical affective and non-affective psychotic symptoms

Poster A29, Thursday, October 20, 11:30 am - 1:00 pm, Le Baron

Ulrich Reininghaus1,2; 1Department of Psychiatry and Psychology, School for Mental Health and Neuroscience, Maastricht University, The Netherlands, 2Centre for Epidemiology and Public Health, Health Service and Population Research Department, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK

Recent years have seen calls for cross-disorder research that looks across traditional diagnostic boundaries to strengthen the dimensional approach to classification in psychiatry. While the Kraepelinian dichotomy of dementia praecox/schizophrenia and manic depression has informed diagnostic classification since first proposed, it has recently been challenged in light of evidence on shared genetic and socio-environmental contributions to psychosis spectrum disorders. However, empirical efforts to identify a more fundamental, transdiagnostic phenotype of psychosis remain remarkably limited. This talk will present findings from a series of analyses to investigate whether psychotic disorders lie on a transdianostic spectrum with overlapping non-affective and affective psychotic symptoms. Multidimensional item response modelling on symptom ratings of the Positive and Negative Syndrome Scale indicated that there is one transdiagnostic psychosis dimension underlying affective and non-affective psychotic symptoms in early and enduring schizophrenia spectrum disorder. More recent analyses on symptom ratings of the OPCRIT system further indicated that the transdiagnostic psychosis dimension cuts across boundaries of the Kraepelinian dichotomy, suggesting that schizophrenia and bipolar disorder lie on a psychosis spectrum with overlapping non-affective and affective symptoms. This transdiagnostic psychosis phenotype has now also been shown to extend to subclinical symptom levels in the general population. Our findings suggest that psychotic disorders lie on a transdiagnostic spectrum with overlapping affective and non-affective symptoms. Coupled with strong evidence on diagnostic utility, this should inform inclusion of dimensional approaches into classification systems and provides a directly measurable phenotype for cross-disorder investigations into shared genetic and environmental factors of psychosis.

Topic Area: Diagnosis and Phenomenology

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