Substance use disorders linked to conversion to schizophrenia

(HealthDay)—Substance use disorders are associated with conversion from schizotypal disorder to schizophrenia, according to a study published online April 25 in JAMA Psychiatry.

Carsten Hjorthøj, Ph.D., from Copenhagen University Hospital in Denmark, and colleagues conducted a prospective cohort study which included a population-based sample of 2,539 individuals born in Denmark with an incident diagnosis of schizotypal disorder and without a previous diagnosis of schizophrenia.

The researchers found that 16.3 percent of the study participants experienced conversion to schizophrenia after two years. After 20 years, the conversion rate was 33.1 and 58.2 percent overall and among those with cannabis use disorders, respectively. Any substance use disorder was correlated with conversion to schizophrenia in fully-adjusted models (hazard ratio, 1.34). On stratification by substance, there were correlations for conversion to schizophrenia for cannabis use disorders, amphetamine use disorders, and opioid use disorders (hazard ratios, 1.3, 1.9, and 2.74, respectively). Concurrent use of antipsychotics, functional level before incident schizotypal disorder, or parental history of mental disorders did not explain these correlations.

"Conversion rates are high even in those without substance use disorders, indicating a need for universal and substance-targeted prevention in individuals with schizotypal disorder," the authors write.