Cannabis Use Thins the Brain's Frontal Cortex in Young Adults, With Distinct Effects in Those With ADHD
Young adult cannabis users showed decreased cortical thickness in multiple frontal brain regions rich in cannabinoid receptors, while earlier onset of use in those with ADHD was associated with a different pattern of cortical changes.
Quick Facts
What This Study Found
Researchers compared brain structure in young adults with and without childhood ADHD who did or did not use cannabis regularly. After controlling for age, gender, brain size, nicotine, and binge drinking, cannabis use was associated with decreased cortical thickness in several brain regions.
Specifically, cannabis users (regardless of ADHD status) had thinner cortex in the right superior frontal sulcus, anterior cingulate, isthmus of the cingulate gyrus, and left superior frontal and precentral regions. These areas are rich in cannabinoid receptors and involved in cognitive control.
Interestingly, ADHD diagnosis alone did not predict brain structure, but persistent ADHD (symptoms continuing into adulthood) was associated with thinner cortex in regions controlling movement and inhibition. For cannabis users with ADHD specifically, earlier onset of regular cannabis use predicted a different pattern of cortical changes.
Key Numbers
Four groups: ADHD+cannabis (n=37), ADHD-only (n=44), cannabis-only (n=18), controls (n=21). Cannabis users: decreased cortical thickness in 5 frontal/cingulate regions. Persistent ADHD: decreased left precentral/postcentral thickness. All effects controlled for nicotine and binge drinking.
How They Did This
Cross-sectional MRI study comparing four groups: ADHD with cannabis use (n=37), ADHD without use (n=44), non-ADHD cannabis users (n=18), and non-ADHD non-users (n=21). Multiple regression and MANCOVA controlled for age, gender, total brain volume, nicotine, and binge drinking.
Why This Research Matters
ADHD is a major risk factor for cannabis use, and many young people with ADHD use cannabis. This study shows that cannabis affects brain structure in regions important for the very cognitive functions (attention, inhibition) that are already compromised in ADHD, suggesting a potential compounding effect.
The Bigger Picture
The convergence of cannabis effects and ADHD vulnerability in frontal brain regions suggests that cannabis use in ADHD populations may be particularly concerning for cognitive development. However, longitudinal studies are needed to determine if cannabis causes thinning or if thinner cortex predisposes to cannabis use.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine causality. Groups were unequal in size. Cannabis use was self-reported. Could not control for all potential confounders (e.g., socioeconomic status, other substance use). Earlier cannabis onset in ADHD may reflect ADHD severity rather than a cannabis-specific effect.
Questions This Raises
- ?Does cortical thinning from cannabis use worsen ADHD symptoms?
- ?Would the brain changes reverse with abstinence?
- ?Is the interaction between ADHD and cannabis onset age clinically significant for treatment decisions?
Trust & Context
- Key Stat:
- Cannabis users had thinner cortex in 5 frontal regions rich in cannabinoid receptors
- Evidence Grade:
- MRI study with multiple groups and extensive confound control, but cross-sectional design and modest sample sizes limit causal conclusions.
- Study Age:
- Published in 2016. Neuroimaging research on cannabis and ADHD continues to evolve with larger longitudinal studies.
- Original Title:
- The impact of ADHD persistence, recent cannabis use, and age of regular cannabis use onset on subcortical volume and cortical thickness in young adults.
- Published In:
- Drug and alcohol dependence, 161, 135-46 (2016)
- Authors:
- Lisdahl, Krista M(13), Tamm, Leanne(5), Epstein, Jeffery N(6), Jernigan, Terry, Molina, Brooke S G, Hinshaw, Stephen P, Swanson, James M, Newman, Erik, Kelly, Clare, Bjork, James M
- Database ID:
- RTHC-01213
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis thin the brain?
In this study, young adult cannabis users had thinner cortex in frontal brain regions rich in cannabinoid receptors, even after controlling for alcohol, nicotine, and other factors. Whether cannabis causes this or people with thinner cortex are more likely to use remains unclear.
Is cannabis worse for people with ADHD?
Cannabis affected brain regions involved in attention and inhibition, which are already compromised in ADHD. Earlier cannabis use onset in ADHD was associated with distinct cortical changes, suggesting potential compounding effects.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-01213APA
Lisdahl, Krista M; Tamm, Leanne; Epstein, Jeffery N; Jernigan, Terry; Molina, Brooke S G; Hinshaw, Stephen P; Swanson, James M; Newman, Erik; Kelly, Clare; Bjork, James M. (2016). The impact of ADHD persistence, recent cannabis use, and age of regular cannabis use onset on subcortical volume and cortical thickness in young adults.. Drug and alcohol dependence, 161, 135-46. https://doi.org/10.1016/j.drugalcdep.2016.01.032
MLA
Lisdahl, Krista M, et al. "The impact of ADHD persistence, recent cannabis use, and age of regular cannabis use onset on subcortical volume and cortical thickness in young adults.." Drug and alcohol dependence, 2016. https://doi.org/10.1016/j.drugalcdep.2016.01.032
RethinkTHC
RethinkTHC Research Database. "The impact of ADHD persistence, recent cannabis use, and age..." RTHC-01213. Retrieved from https://rethinkthc.com/research/lisdahl-2016-the-impact-of-adhd
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.