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Psychiatry Clin Neurosci. 2013 Nov;67(7):483-92. doi: 10.1111/pcn.12085. Epub 2013 Sep 30.

Is cannabis neurotoxic for the healthy brain? A meta-analytical review of structural brain alterations in non-psychotic users.

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Department of Psychosis Studies, Institute of Psychiatry, King's College London, London, UK; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.



Despite growing research in the field of cannabis imaging, mostly in those with a psychotic illness, the possible neurotoxic effects of smoked cannabis on the healthy brain have yet to be fully understood. There appears to be a need to evaluate the existing imaging data on the neuroanatomical effects of cannabis use on non-psychotic populations.


We conducted a meta-analytical review to estimate the putative neurotoxic effect of cannabis in non-psychotic subjects who were using or not using cannabis. We specifically tested the hypothesis that cannabis use can alter grey and white matter in non-psychotic subjects.


Our systematic literature search uncovered 14 studies meeting the inclusion criteria for the meta-analysis. The overall database comprised 362 users and 365 non-users. At the level of the individual studies there is limited and contrasting evidence supporting a cannabis-related alteration on the white and grey matter structures of non-psychotic cannabis users. However, our meta-analysis showed a consistent smaller hippocampus in users as compared to non-users. Heterogeneity across study designs, image acquisition, small sample sizes and limited availability of regions of interest to be included in the meta-analysis may undermine the core findings of this study.


Our results suggest that in the healthy brain, chronic and long-term cannabis exposure may exert significant effects in brain areas enriched with cannabinoid receptors, such as the hippocampus, which could be related to a neurotoxic action.


amygdala; cannabis; hippocampus; neuroimaging; psychosis

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