Characterizing psychosis-relevant phenomena and cognitive function in a unique population with isolated, chronic and very heavy cannabis exposure
Psychological Medicine October 16, 2019 D. D’souza, S. Ganesh, J. Cortes-Briones et al.
Heavy, chronic cannabis use that begins early and is not accompanied by other drugs is associated with more psychosis-relevant symptoms and poorer cognitive performance. Users averaged over 30,000 lifetime cannabis exposures and scored higher on the Schizotypal Personality Questionnaire (mean 24 vs. 13) and lower on a composite cognitive test (mean -0.23 vs. +0.28) compared to matched non-user controls. Moderate to large deficits appeared in attention, psychomotor speed, working memory, cognitive flexibility, visuo-spatial processing, and verbal memory. A subsample of users also showed worse outcomes than their non-using siblings.