Risk and associated factors for a future schizophrenia diagnosis after an index diagnosis of unspecified psychotic disorder: A population-based study

A significant minority of unspecified psychosis presentations progress to schizophrenia. Clinical risk factors can inform targeted referral to specialized treatment programs, but few population studies have examined this. In this study, we used health administrative data for a population-based cohort from Manitoba, Canada to characterize the risk and identify vulnerable subgroups for a future diagnosis of schizophrenia after a diagnosis of unspecified psychotic disorder. Individuals aged 13-60 years with an inpatient or outpatient diagnosis of unspecified psychotic disorder between April 1, 2007 and March 31, 2012, and without any prior diagnosis of schizophrenia or related disorder, were identified (N = 3, 289). The primary outcome was a diagnosis of schizophrenia recorded after the index diagnosis of unspecified psychotic disorder and before March 31, 2015. Adjusted hazard ratios were computed controlling for age, sex, urbanicity, income, prior diagnosis of unspecified psychotic disorder, provider making the diagnosis, prior 12-month psychiatric hospitalization, and prior 12-month diagnoses of mood, anxiety, substance use, or personality disorders, and substance-induced psychosis. A classification tree identified vulnerable subgroups. The cumulative risk of a future diagnosis of schizophrenia was 26% during the follow-up period (mean 4.5 years), with a mean time to diagnosis of 2.0 years. The most vulnerable subgroup was diagnosed by a psychiatrist, younger than 27 years, without a mood or anxiety disorder, male, and residing in a low-income neighborhood; the rate of a subsequent schizophrenia diagnosis was 61.2%. These results support that identification of specific sociodemographic and clinical factors can help clinicians counsel and intervene with those at highest risk.