OverviewThe brain effects of marijuana use is a rapidly increasing area of neuroscience. This study specifically addressed changes in brain volume using MRI. Brain scans of marijuana users were compared to those of nonusers to determine differences in response to substance use. Results demonstrated marijuana users had decreased orbitofrontal gyri volume bilaterally (frontal lobe) and increased functional and structural connectivity in the orbitofrontal cortex (OFC) network, a brain region rich in cannabis receptors. More differences can be seen among marijuana users, with individuals who started using cannabis at a younger age having higher, more increased functional activity in the OFC network. As this study is just the beginning of identifying brain changes following marijuana use, follow-up longitudinal studies would be necessary to determine a causal relationship between marijuana and these observed effects.
Figure 1. Group comparison of the gray matter volume by SPM8 plus DARTEL analysis demonstrates significant reduction of gray matter volume in bilateral orbitofrontal gyri (AAL atlas) in marijuana users compared with controls. Right side of the image represents the right hemisphere in axial view.