Rates and Predictors of Conversion to Schizophrenia or Bipolar Disorder Following Substance-Induced Psychosis.
Level 3 - non-randomized controlled study
Nationwide registry-based observational cohort study
PubMed 29179576 · doi:10.1176/appi.ajp.2017.17020223
What was done
Researchers tracked all individuals in the Danish Civil Registration System and Psychiatric Central Research Register diagnosed with substance-induced psychosis between 1994 and 2014 (N=6,788). Cohort members were followed until conversion to schizophrenia or bipolar disorder, death, emigration, or August 2014. Cumulative conversion probabilities were estimated via Kaplan-Meier analysis, and hazard ratios for predictors were calculated using Cox proportional hazards regression.
What was found
Overall, 32.2% (95% CI=29.7-34.9) of patients converted to either schizophrenia-spectrum disorders or bipolar disorder. Cannabis-induced psychosis carried the highest conversion rate at 47.4% (95% CI=42.7-52.3). Young age predicted higher risk of conversion to schizophrenia, and subsequent self-harm was significantly associated with conversion to both schizophrenia and bipolar disorder. Half of all conversions occurred within 3.1 years for schizophrenia and within 4.4 years for bipolar disorder.
Why it matters
Substance-induced psychosis often represents an early manifestation of primary severe psychiatric illness rather than a self-limiting episode, particularly following cannabis use. Because half of conversions take 3 to 4 years to emerge, clinical monitoring must extend well beyond the acute presentation.
Limits
The study is restricted to Danish registry data and hospital/specialist psychiatric diagnoses, which may not capture milder cases managed purely in primary care or individuals who did not seek medical attention. Specific substance doses, frequency, poly-substance details, and unmeasured psychosocial confounders were not described in the abstract.
Cited by
- supports Young males with a predisposition to psychosis or bipolar disorder who use cannabis can trigger non-recovering psychotic episodes.