We investigated the morphology of multiple brain regions in a rare sample of
15 very heavy cannabis users with minimal psychiatric comorbidity or
significant exposure to other substances (compared with 15 age- and
IQ-matched non-cannabis-using controls) using manual techniques. Heavy
cannabis users demonstrated smaller hippocampus and amygdala volumes, but no
alterations of the orbitofrontal and anterior- and paracingulate cortices,
or the pituitary gland. These findings indicate that chronic cannabis use
has a selective and detrimental impact on the morphology of the
mediotemporal lobe.