In terms of structural findings, specific regional brain analyses demonstrated evidence of structural abnormalities when adult chronic cannabis users were compared with healthy controls. The most consistently reported brain alteration was reduced hippocampal volume [145], [146], [148], [149], which was shown to persist even after several months of abstinence in one study [145] and also to be related to the amount of cannabis use [145], [146], [149]. Other frequently reported morphological brain alterations related to chronic cannabis use were reported in the amygdala [146], [149], [156], the cerebellum [146], [155] and the frontal cortex [148], [154]. Lastly, two DTI studies found differences in the mean diffusivity or fractional anisotropy in the corpus callosum and the frontal white matter fibre tract [144], [147], suggesting that chronic cannabis exposure may also alter white matter structural integrity, by either affecting demyelination or causing axonal damage or indirectly through delaying normal brain development. With regard to the few structural MRI studies focusing on the effects of cannabis use on brain morphology in adolescents, some discrepancies were reported related to adult population. These inconsistencies may
