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Psychotic-Like Experiences and Cannabis Use

JAMA Psychiatry; ePub 2018 Oct 17; Karcher, et al

Despite the strong contribution of shared genetic factors, frequent and problem cannabis use also appears to be associated with psychotic-like experiences (PLEs) via person-specific pathways, a recent study found. This study’s findings suggest that policy discussions surrounding legalization should consider the influence of escalations in cannabis use on trait-like indices of vulnerability, such as PLEs, which could contribute to pervasive psychological and interpersonal burden. In this cross-sectional analysis, diagnostic interviews and self-reported data were collected from 2 separate population-based samples of twin and non-twin sibling pairs. The study included data from 1,188 Human Connectome Project participants and 3,486 ATR3 participants, totaling 4,674 participants. Researchers found:

  • Psychotic-like experiences were associated with frequent cannabis use (β=0.11), cannabis use disorder (β=0.13), and current cannabis use (β=0.07) even after adjustment for covariates.
  • Correlated genetic factors explained between 69.2% and 84.1% of this observed association.
  • Within discordant pairs of twins/siblings (Npairs, 308-324), psychotic-like experiences were more common in cannabis-exposed individuals compared with their relative who used cannabis to a lesser degree (β ≥ .23; eg, frequent and infrequent cannabis-using relatives significantly differed, z = −5.41).


Karcher NR, Barch DM, Demers CH, et al. Genetic predisposition vs individual-specific processes in the association between psychotic-like experiences and cannabis use. [Published online ahead of print October 17, 2018]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2018.2546.