Cannabis is the most widely used illicit drug worldwide, though it is unclear whether its regular use is associated with persistent
alterations in brain morphology. This review examines evidence from human structural neuroimaging investigations of regular cannabis
users and focuses on achieving three main objectives. These include examining whether the literature to date provides evidence that
alteration of brain morphology in regular cannabis users: i) is apparent, compared to non-cannabis using controls; ii) is associated with
patterns of cannabis use; and with iii) measures of psychopathology and neurocognitive performance. The published findings indicate
that regular cannabis use is associated with alterations in medial temporal, frontal and cerebellar brain regions. Greater brain morphological
alterations were evident among samples that used at higher doses for longer periods. However, the evidence for an association between
brain morphology and cannabis use parameters was mixed. Further, there is poor evidence for an association between measures of
brain morphology and of psychopathology symptoms/neurocognitive performance. Overall, numerous methodological issues characterize
the literature to date. These include investigation of small sample sizes, heterogeneity across studies in sample characteristics (e.g., sex,
comorbidity) and in employed imaging techniques, as well as the examination of only a limited number of brain regions. These factors
make it difficult to draw firm conclusions from the existing findings. Nevertheless, this review supports the notion that regular cannabis
use is associated with alterations of brain morphology, and highlights the need to consider particular methodological issues when planning
future cannabis research.
Keywords: Cannabis, brain, sMRI, hippocampus, amygdala, prefrontal cortex, cerebellum.
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