This just in: No difference was found in the brains of very heavy marijuana smokers compared to nonusers. More evidence that nullifies the neoprohibitionists' assertions that THC is "neurotoxic" and causes "brain changes" associated with "mental illness." Science slays reefer madness once again. Brain Topogr. 2013 Apr 19. [Epub ahead of print]Combined Grey Matter VBM and White Matter TBSS Analysis in Young First Episode Psychosis Patients With and Without Cannabis Consumption.Haller S, Curtis L, Badan M, Bessero S, Albom M, Chantraine F, Alimenti A, Lovblad KO, Giannakopoulos P, Merlo M.SourceService neuro-diagnostique et neuro-interventionnel DISIM, University Hospitals of Geneva, Rue Gabrielle Perret-Gentil 4, 1211, Geneva 14, Switzerland, email@example.com. Abstract: Cannabis consumption is temporally associated with the development of first episode psychosis FEP. Whether or not the chronic use of this substance induces structural brain changes that may be responsible for the cognitive and psychological disturbances in this disorder is still matter of debate. To address this issue, we compared the magnetic resonance imaging MRI-assessed grey GM and white matter WM changes in young FEP patients between users versus non-users of cannabis. This prospective study included 50 consecutive FEP subjects: 33 users 22.7 ± 4.1 years, 4 women and 17 non-users 23.9 ± 4.2 years, 10 women. Users were further divided into 15 heavy 23.3 ± 4.5 years, 2 women and 18 light users 22.2 ± 3.8 years, 2 women according to their lifetime cannabis use. Voxel-based-morphometry VBM analysis of GM and tract-based-spatial-statistics TBSS analysis of WM were performed. Age and gender were used as non-explanatory co-regressors. There were no supra-threshold differences between user and non-user groups for both GM and WM parameters. This was also the case when only heavy users were compared to non-users. Multivariate models controlling for age and gender confirmed these findings. We found no evidence for cannabis consumption related alterations in GM or WM in FEP subjects. Due to the strict correction for multiple comparisons and sample size, we cannot formally exclude subtle morphometric changes associated with cannabis consumption. However, even if present, such potential alterations would be of low magnitude.