Grant: Doctoral: Vanier Canada Graduate Scholarships

Cannabis use is common in psychotic disorders, especially among young people experiencing a first episode of psychosis. Cannabis is linked to the development of temporary, 'induced' psychotic symptoms, which are caused by cannabis use and diminish with abstinence (cannabis-induced psychosis), while individuals with primary psychosis who also frequently use cannabis (cannabis-comorbid psychosis) have a distinct mental illness requiring a different treatment approach. However, the similarity of the symptoms of these disorders often renders them indistinguishable, creating barriers to intervention and treatment. Previous attempts to identify differentiating features have been unsuccessful at reliably distinguishing between diagnoses. As such, there is an urgent need to refine the diagnostic tools available to psychosis clinics. Despite the abundance of research identifying cognitive deficits, eye movement abnormalities, and speech deficits as core neuropsychological symptoms of primary psychotic disorders (e.g., schizophrenia), limited research has examined these well-established markers as potential methods to improve diagnosis in first-episode psychosis. The proposed novel line of research will assess first-episode psychosis patients upon entry to a psychosis clinic using cognitive, visual, and speech tasks. Participants will be re-assessed at 3-, 6-, and 12-month follow-up time points to evaluate if assessments at baseline can predict diagnostic classification reliably over time. These objective, well-replicated methods are hypothesized to increase accurate diagnosis above and beyond traditionally used measures. The ability to reliably differentiate these disorders is crucial to early intervention in psychosis and holds promise to reduce the diagnostic load on mental health care workers. This research will facilitate more rapid and successful intervention, promote individualized treatment plans, and lead to widespread benefits for patients.