Among 74 young people, cannabis use affected brain volume differently by sex: females showed greater volume while males showed less, and higher aerobic fitness was linked to greater brain volume regardless of cannabis use.
Neuroscience researchers, adolescent health specialists, exercise physiologists
Female cannabis users showed greater brain volume while males showed less compared to same-sex controls
What the researchers found
No overall brain volume differences were found between cannabis users and controls, but sex-by-cannabis interactions revealed that female users had greater frontal and temporal volumes while male users had less volume compared to same-sex controls. Higher aerobic fitness was positively associated with frontal, parietal, cerebellum, and caudate volumes.
Why it matters
The sex-specific effects on brain volume may help explain inconsistent findings in the cannabis neuroimaging literature, while the fitness association suggests aerobic exercise could potentially buffer against cannabis-related brain changes.
The numbers in context
74 participants (36 users, 38 controls); 3 weeks monitored abstinence; sex-by-cannabis interactions in frontal, temporal, and paracentral volumes; female users had greater volume, male users had less; aerobic fitness positively associated with brain volume in multiple regions; abnormal volumes not linked to better cognition.
How the study worked
Cross-sectional study of 74 adolescents and young adults (36 cannabis users, 38 controls) who completed 3 weeks of monitored cannabis abstinence, aerobic fitness testing, structural MRI, and neuropsychological testing.
What this study cannot tell us
Small sample size; cross-sectional design; 3 weeks abstinence may not fully eliminate acute effects; aerobic fitness measured at one time point; directionality of brain volume differences unclear.
How to read the evidence
Small cross-sectional neuroimaging study with monitored abstinence, limited by sample size and cross-sectional design.
When this study was published
Published in 2021 with adolescent and young adult participants.
The bigger picture
The finding that aerobic fitness is associated with greater brain volume opens a potential intervention avenue, suggesting exercise programs might promote neurocognitive health in young cannabis users.
Questions still open
- Would aerobic exercise interventions improve brain outcomes in young cannabis users? Why do female and male cannabis users show opposite brain volume patterns?
Common questions
Does cannabis shrink the brain?
Can exercise protect the brain from cannabis effects?
Read the original research
Cannabis Use and Brain Volume in Adolescent and Young Adult Cannabis Users: Effects Moderated by Sex and Aerobic Fitness.
Journal of the International Neuropsychological Society : JINS, 27(6), 607-620
Citation
Sullivan, Ryan M; Wallace, Alexander L; Wade, Natasha E; Swartz, Ann M; Lisdahl, Krista M. (2021). Cannabis Use and Brain Volume in Adolescent and Young Adult Cannabis Users: Effects Moderated by Sex and Aerobic Fitness.. Journal of the International Neuropsychological Society : JINS, 27(6), 607-620. https://doi.org/10.1017/S135561772100062X
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