We conducted a systematic review to assess the evidence for specific effects of cannabis on impulsivity, disinhibition and motor
control. The review had a specific focus on neuroimaging findings associated with acute and chronic use of the drug and covers literature
published up until May 2012. Seventeen studies were identified, of which 13 met the inclusion criteria; three studies investigated
acute effects of cannabis (1 fMRI, 2 PET), while six studies investigated non-acute functional effects (4 fMRI, 2 PET), and four studies
investigated structural alterations. Functional imaging studies of impulsivity studies suggest that prefrontal blood flow is lower in chronic
cannabis users than in controls. Studies of acute administration of THC or marijuana report increased brain metabolism in several brain
regions during impulsivity tasks. Structural imaging studies of cannabis users found differences in reduced prefrontal volumes and white
matter integrity that might mediate the abnormal impulsivity and mood observed in marijuana users. To address the question whether impulsivity
as a trait precedes cannabis consumption or whether cannabis aggravates impulsivity and discontinuation of usage more longitudinal
study designs are warranted.
Keywords: Cannabis, marijuana, cannabinoids, impulsivity, inhibition, neuroimaging, magnetic resonance imaging, MRI, fMRI.
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