Elevated schizotypy relates to similar cognitive attenuations as seen in psychosis and
cannabis/polydrug use. Also, in schizotypal populations cannabis and polydrug (including
licit drug) use are enhanced.These cognitive attenuations may therefore either be a behavioral
marker of psychotic (-like) symptoms or the consequence of enhanced drug use in
schizotypal populations.To elucidate this, we investigated the link between cognitive attenuation
and cannabis use in largely pure cannabis users (35) and non-using controls (48),
accounting for the potential additional influence of both schizotypy and licit drug use (alcohol,
nicotine). Cognitive attenuations commonly seen in psychosis were associated with
cannabis and alcohol use, but not schizotypy. Future studies should therefore consider
(i) non-excessive licit substance use (e.g., alcohol) in studies investigating the effect of
cannabis use on cognition and (ii) both enhanced illicit and licit substance use in studies
investigating cognition in schizotypal populations.