Early cannabis use and schizotypal personality disorder symptoms from adolescence to middle adulthood.

BACKGROUND While increasing evidence suggests that cannabis use may play a role in the development of schizophrenia in some young people, less is known about the strength and specificity of its relationship to latent schizophrenia liability, i.e., schizotypal personality disorder traits. AIMS Determine the predictive value of cannabis use during childhood and early adolescence on schizotypal personality disorder (SPD) symptoms projecting into adulthood, using a community-based longitudinal cohort from upstate New York. METHOD Prospective data from 804 participants was used to determine associations between early cannabis use and later schizotypal symptoms, accounting for important potential confounds (e.g., adolescent schizotypal symptoms). RESULTS Cannabis use with onset prior to age 14 strongly predicted SPD symptoms in adulthood, independent of early adolescent SPD symptoms, major depression, anxiety disorder, other drug use, and cigarette use. There was no interaction effect of early cannabis use and early adolescent SPD symptoms on SPD symptoms into adulthood. CONCLUSIONS Our data provide further support for a strong association of early cannabis use with the development of symptoms characteristic of schizophrenia spectrum disorders. As with studies in schizophrenia, early SPD symptoms could not fully explain the association of early cannabis use with later schizotypal symptoms. The mechanisms that underlie the association of cannabis use and schizotypal symptoms in a developmental context deserve further exploration.