A meta-analysis found no major brain volume differences in cannabis-using teens, but age and sex modulated subtle effects
A meta-analysis of 6 brain imaging studies found no significant gray matter volume differences between cannabis-using and non-using youth overall, but age and sex influenced the pattern of subtle differences.
Quick Facts
What This Study Found
No regions showed significant gray matter volume differences between 357 cannabis-using and 404 typically developing youth. Meta-regressions revealed age effects in the superior temporal gyrus (older users showed decreased, younger users increased volume). A higher proportion of females was associated with increased volume in the middle occipital gyrus in users vs. controls.
Key Numbers
6 VBM studies, 357 cannabis users (mean age 16.68, 71% male), 404 controls (mean age 16.77, 63% male). No significant main effect. Age moderated STG differences. Sex moderated middle occipital gyrus differences.
How They Did This
Systematic review (1,326 citations, 24 included qualitatively) with seed-based d mapping (SDM) meta-analysis of 6 whole-brain VBM studies. Meta-regressions examined effects of age, sex, and cannabis use duration on gray matter volume differences.
Why This Research Matters
This meta-analysis challenges the assumption of dramatic brain volume changes from adolescent cannabis use, while highlighting that developmental timing and sex may determine where and how subtle effects emerge.
The Bigger Picture
The null main finding is notable: structural brain volume changes from adolescent cannabis use, if they exist, appear subtle and context-dependent rather than dramatic and universal.
What This Study Doesn't Tell Us
Only 6 studies met strict inclusion criteria. Studies varied in cannabis use definitions and covariates. VBM methodology may miss subtle or regional-specific changes. Meta-regression with few studies has limited power.
Questions This Raises
- ?Do other neuroimaging methods (cortical thickness, diffusion tensor imaging) show effects that VBM misses?
- ?Would larger studies with more detailed cannabis exposure data reveal consistent patterns?
- ?Are the age-dependent effects reflecting developmental timing?
Trust & Context
- Key Stat:
- No significant overall brain volume difference between teen cannabis users and controls
- Evidence Grade:
- Systematic meta-analysis following PRISMA guidelines, but limited by few eligible studies and heterogeneous cannabis exposure measures.
- Study Age:
- 2021 meta-analysis. Provides a balanced perspective on adolescent cannabis neuroimaging findings.
- Original Title:
- Age- and Sex-Related Cortical Gray Matter Volume Differences in Adolescent Cannabis Users: A Systematic Review and Meta-Analysis of Voxel-Based Morphometry Studies.
- Published In:
- Frontiers in psychiatry, 12, 745193 (2021)
- Authors:
- Allick, Aliyah(2), Park, Grace(2), Kim, Kwon(2), Vintimilla, Michelle, Rathod, Krutika, Lebo, Rachael, Nanavati, Julie, Hammond, Christopher J
- Database ID:
- RTHC-02957
Evidence Hierarchy
Combines results from multiple studies to find an overall pattern.
What do these levels mean? →Frequently Asked Questions
Does cannabis change teen brain structure?
This meta-analysis found no significant overall gray matter volume differences. However, subtle effects varied by age and sex, suggesting the relationship is more nuanced than commonly portrayed.
Why do some studies find brain differences and this meta-analysis doesn't?
Individual studies may detect region-specific effects. When pooled across studies with different methods and populations, these effects may cancel out or fall below statistical thresholds.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-02957APA
Allick, Aliyah; Park, Grace; Kim, Kwon; Vintimilla, Michelle; Rathod, Krutika; Lebo, Rachael; Nanavati, Julie; Hammond, Christopher J. (2021). Age- and Sex-Related Cortical Gray Matter Volume Differences in Adolescent Cannabis Users: A Systematic Review and Meta-Analysis of Voxel-Based Morphometry Studies.. Frontiers in psychiatry, 12, 745193. https://doi.org/10.3389/fpsyt.2021.745193
MLA
Allick, Aliyah, et al. "Age- and Sex-Related Cortical Gray Matter Volume Differences in Adolescent Cannabis Users: A Systematic Review and Meta-Analysis of Voxel-Based Morphometry Studies.." Frontiers in psychiatry, 2021. https://doi.org/10.3389/fpsyt.2021.745193
RethinkTHC
RethinkTHC Research Database. "Age- and Sex-Related Cortical Gray Matter Volume Differences..." RTHC-02957. Retrieved from https://rethinkthc.com/research/allick-2021-age-and-sexrelated-cortical
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.