Reducing Diagnostic Uncertainty in First-Episode Psychosis: A Neuropsychological Approach to Differentiating between Cannabis-Induced and Primary Psychotic Disorders
Background: Cannabis use is highly comorbid with psychotic disorders, especially among young people experiencing their first episode of psychosis. The high rate of cannabis use in this population has led to uncertainty between diagnoses of cannabis-induced psychosis and primary psychosis, often with cannabis comorbidity (primary psychosis). The similarity of the clinical presentations of these disorders often renders them indistinguishable, creating difficulties in intervention and treatment. Attempts to identify differentiating features have been variable and narrow in scope, with a focus limited to self-report, patient history, and symptoms. Despite the abundance of research identifying cognitive deficits and abnormalities in eye movements and speech as core biological and neurological symptoms of primary psychotic disorders (e.g., schizophrenia), limited research has pursued such biomarkers as potential targets for differentiation in first-episode psychosis. Purpose: The current study aimed to assess individuals diagnosed with either cannabis-induced or primary psychosis using cognitive, visual processing, eye movement, and speech tasks, which are each associated with well-recognized and specific deficits in primary psychotic disorders. Method: Sixteen participants with cannabis-induced psychosis and twelve participants with primary psychosis were recruited in the Kingston, Ontario community. Cognitive performance, backward visual masking, pro- and anti-saccade eye movements, and semantic coherence were assessed for the first time in this population, alongside clinical symptoms, trauma, substance use, premorbid functioning, and illness insight. Results. Relative to individuals with primary psychosis, individuals with cannabis-induced psychosis demonstrated significantly better performance on the pro-saccade task, a faster reaction time on both the pro- and anti-saccade task, more coherent speech, better premorbid adjustment, more cannabis use, and a higher degree of insight into their illness. The use of these variables in a discriminant analysis successfully classified cases with 88.5% accuracy. The ability to reliably differentiate these disorders is crucial to early intervention and treatment in first-episode psychosis.
URI for this recordhttp://hdl.handle.net/1974/26533
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