The cumulative use of cannabis over several decades is not associated with a significantly elevated risk of either psychiatric disorders, cognitive decline, or other adverse psychosocial outcomes, according to longitudinal data published in the Journal of Psychopathology and Clinical Science.
Investigators affiliated with the University of Minnesota and the University of Colorado assessed the long-term impact of cannabis use on psychiatric and psychosocial outcomes in a sample of more than 4,000 adult twins. “This study suggests that lifetime exposure to cannabis has few persistent effects on mental health and other psychosocial outcomes,” researchers reported. “We did not identify within-pair differences in cognitive ability. …Cannabis consumption did not predict within-pair differences in psychoticism.”
The study’s authors concluded: “Broadly speaking, our results do not support a causal relationship between lifetime average cannabis frequency and most of the substance use, psychiatric, and psychosocial outcomes assessed here. Rather, genetic and familial confounding most likely explain the relationships between cannabis use and the negative outcomes associated with it.”
