title: Is cannabis neurotoxic for the healthy brain? A meta-analytical review of structural brain alterations in non-psychotic users.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, King's College London, London, UK; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Rocchetti
authors.forename: Alessandra
authors.initials: A
authors.lastname: Crescini
authors.forename: Stefan
authors.initials: S
authors.lastname: Borgwardt
authors.forename: Edgardo
authors.initials: E
authors.lastname: Caverzasi
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Politi
authors.forename: Zerrin
authors.initials: Z
authors.lastname: Atakan
authors.forename: Paolo
authors.initials: P
authors.lastname: Fusar-Poli
mesh_terms: D001921:Brain / Q000187:drug effects* / Q000473:pathology; D002188:Cannabis / Q000009:adverse effects*; D006801:Humans; D008385:Marijuana Smoking / Q000009:adverse effects*; D020258:Neurotoxicity Syndromes / Q000473:pathology*; D010549:Personal Satisfaction
keywords: amygdala; cannabis; hippocampus; neuroimaging; psychosis