Despite speculation regarding neurotoxic effects of tetrahydrocannabinol based on preclinical research (e.g.38,39), the observed cannabis-related volumetric differences were well within the range of normal variation. When using a simple index of exposure (i.e. ever vs. never use), we found no evidence for the causal influence of cannabis exposure on amygdala volume. Future work characterizing the roles of causal and predispositional factors underpinning neural changes at various degrees of cannabis involvement may provide targets for substance abuse policy and prevention programs.
