Cannabis and nicotine had opposite effects on brain cortex thickness in teens and young adults
Among 223 young people aged 16-22, both cannabis and nicotine users had thinner frontal cortices than non-users, but in those who used both substances, cannabis appeared to partially offset nicotine-related thinning.
Quick Facts
What This Study Found
Both cannabis and nicotine users had thinner frontal cortices bilaterally compared to non-users. However, an interaction effect was observed: in three left frontal regions, cannabis use was associated with thicker cortices among those with a history of nicotine use, suggesting cannabis may partially offset nicotine-related cortical thinning.
Key Numbers
223 participants aged 16-22; 11 bilateral frontal cortical regions examined; interaction effects found in 3 left frontal regions; both substances independently associated with thinner cortices
How They Did This
Cross-sectional study using structural MRI to measure cortical thickness in 11 bilateral frontal regions among 223 participants aged 16-22. Linear regression models examined main and interactive effects of past-year nicotine and cannabis use on gray matter thickness.
Why This Research Matters
Cannabis and nicotine are frequently co-used by young people, yet most brain studies examine them separately. Understanding how these substances interact during a critical period of brain development has important implications for public health messaging.
The Bigger Picture
The interaction between cannabis and nicotine on brain structure suggests studying either substance in isolation may miss important combined effects, especially given how commonly they are used together by young people.
What This Study Doesn't Tell Us
Cross-sectional design cannot determine causality or temporal sequence; cortical thickness differences may precede substance use; cannot rule out other substance use or confounders; self-reported use data
Questions This Raises
- ?What mechanism could explain cannabis offsetting nicotine-related cortical thinning?
- ?Do these structural differences translate into functional or cognitive differences?
Trust & Context
- Key Stat:
- 223 participants aged 16-22 scanned with MRI
- Evidence Grade:
- Cross-sectional neuroimaging study with appropriate statistical modeling but unable to establish causality or temporal direction.
- Study Age:
- 2024 study
- Original Title:
- The Combined Effects of Nicotine and Cannabis on Cortical Thickness Estimates in Adolescents and Emerging Adults.
- Published In:
- Brain sciences, 14(3) (2024)
- Authors:
- Hernandez Mejia, Margie(2), Courtney, Kelly E(6), Wade, Natasha E(18), Wallace, Alexander, Baca, Rachel E, Shen, Qian, Happer, Joseph Patrick, Jacobus, Joanna
- Database ID:
- RTHC-05374
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
How did cannabis and nicotine affect brain structure differently?
Both substances were independently associated with thinner frontal cortices compared to non-users. But when researchers looked at people who used both substances, cannabis appeared to partially counteract nicotine-related thinning in three left frontal brain regions.
Why does this interaction matter?
Cannabis and nicotine are frequently used together by teens and young adults, but most research examines them separately. This study suggests their combined effects on the developing brain may be different from what either substance does alone.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05374APA
Hernandez Mejia, Margie; Courtney, Kelly E; Wade, Natasha E; Wallace, Alexander; Baca, Rachel E; Shen, Qian; Happer, Joseph Patrick; Jacobus, Joanna. (2024). The Combined Effects of Nicotine and Cannabis on Cortical Thickness Estimates in Adolescents and Emerging Adults.. Brain sciences, 14(3). https://doi.org/10.3390/brainsci14030195
MLA
Hernandez Mejia, Margie, et al. "The Combined Effects of Nicotine and Cannabis on Cortical Thickness Estimates in Adolescents and Emerging Adults.." Brain sciences, 2024. https://doi.org/10.3390/brainsci14030195
RethinkTHC
RethinkTHC Research Database. "The Combined Effects of Nicotine and Cannabis on Cortical Th..." RTHC-05374. Retrieved from https://rethinkthc.com/research/hernandez-2024-the-combined-effects-of
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.