Grey Matter Changes Associated with Heavy Cannabis Use: A Longitudinal sMRI Study

Area of Science:

• Neuroscience
• Psychiatry
• Addiction Research

Background:

• Cannabis is the most widely used illicit substance globally.
• Previous cross-sectional studies suggest cannabis use may impact brain structure, but lack longitudinal data.
• Longitudinal neuroimaging data on cannabis use and brain morphology in young adults is limited.

Purpose of the Study:

• To prospectively investigate the association between continued cannabis use and grey matter volume reductions in young adults.
• To examine if higher levels of cannabis exposure correlate with changes in brain morphology over time.
• To explore the relationship between cannabis use, related problems, and specific regional grey matter volumes.

Main Methods:

• Prospective longitudinal study with a 3-year follow-up.
• Involved heavy cannabis users (N=20) and non-using controls (N=22), aged 20-21 at baseline.
• Utilized T1-structural MRI scans and VBM-8 software for grey matter volume estimation in key brain regions.

Main Results:

• Continued cannabis use showed no significant effect on overall grey matter volume change over the 3-year follow-up period.
• Cross-sectional analyses revealed negative correlations between cannabis use/problems and grey matter volume in the left hippocampus, amygdala, and superior temporal gyrus.
• Findings suggest pre-existing smaller grey matter volumes may be a risk factor for heavy cannabis use or that cannabis effects on grey matter are confined to adolescence.

Conclusions:

• Continued heavy cannabis use in early adulthood does not appear to cause further grey matter reductions.
• Smaller grey matter volumes in medial temporal lobe regions might predispose individuals to heavy cannabis use.
• Further long-term prospective studies beginning in early adolescence are required to definitively understand cannabis's impact on brain development.