Cannabis disrupted brain network connectivity equally in teens and adults, and adding CBD did not make it safer
Vaporized cannabis reduced resting-state brain network connectivity across five major networks in both adolescent and adult semi-regular users, with CBD not counteracting THC's effects and in some cases making disruption worse.
Quick Facts
What This Study Found
Cannabis caused significant reductions in within-network connectivity in the default mode, executive control, salience, hippocampal, and limbic striatal networks compared to placebo. CBD co-administration did not attenuate THC's effects and further reduced connectivity in some networks. Despite age-related baseline differences, there were no interactions between age group and cannabis treatment in any network.
Key Numbers
Executive control network: F[2,88]=18.62, P<0.001, effect size 0.123. Limbic striatal: F[2,88]=16.19, P<0.001, effect size 0.102. Hippocampal: F[2,88]=14.65, P<0.001, effect size 0.087. Salience: F[2,88]=12.12, P<0.001, effect size 0.076. Default mode: F[2,88]=3.97, P=0.022, effect size 0.018. No age-by-treatment interactions in any network.
How They Did This
Double-blind, placebo-controlled fMRI study with vaporized cannabis (placebo, THC 8mg/75kg, THC+CBD 8mg THC + 24mg CBD per 75kg). 22 adolescents (16-17) and 24 young adults (26-29), all semi-regular cannabis users (0.5-3 days/week), matched for use frequency.
Why This Research Matters
Two common assumptions are challenged: that adolescent brains are more vulnerable to acute cannabis effects than adult brains, and that CBD can mitigate THC's disruption of brain function. Neither held up in this controlled study.
The Bigger Picture
The finding that CBD does not counteract and may potentiate THC's brain effects directly challenges marketing of high-CBD cannabis products as "safer." If replicated, this could reshape harm reduction messaging around cannabis product selection.
What This Study Doesn't Tell Us
Semi-regular users only; findings may differ in cannabis-naive individuals or heavy users. Small sample sizes per group. Single acute dose; chronic effects may differ. Resting-state connectivity does not necessarily predict functional outcomes. Specific THC:CBD ratio tested may not generalize.
Questions This Raises
- ?Why did CBD potentiate rather than counteract THC in some networks?
- ?Would different THC:CBD ratios produce different results?
Trust & Context
- Key Stat:
- CBD did not counteract THC brain effects; in some cases made them worse
- Evidence Grade:
- Double-blind placebo-controlled design with objective fMRI outcomes, though small sample sizes limit statistical power for interaction effects.
- Study Age:
- 2024 study
- Original Title:
- Acute effects of different types of cannabis on young adult and adolescent resting-state brain networks.
- Published In:
- Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 49(10), 1640-1651 (2024)
- Authors:
- Ertl, Natalie, Freeman, Tom P(51), Mokrysz, Claire(11), Ofori, Shelan, Borissova, Anna, Petrilli, Kat, Curran, H Valerie, Lawn, Will, Wall, Matthew B
- Database ID:
- RTHC-05296
Evidence Hierarchy
Frequently Asked Questions
Does this mean CBD is harmful?
Not necessarily. The study tested CBD combined with THC in vaporized cannabis, not CBD alone. The finding is specifically that CBD did not make THC safer in terms of brain connectivity disruption, not that CBD itself is harmful.
Are teen brains more affected by cannabis than adult brains?
In this study, the acute effects on brain connectivity were similar in teens and adults. However, this does not address whether repeated exposure during adolescence has different long-term consequences than adult use.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05296APA
Ertl, Natalie; Freeman, Tom P; Mokrysz, Claire; Ofori, Shelan; Borissova, Anna; Petrilli, Kat; Curran, H Valerie; Lawn, Will; Wall, Matthew B. (2024). Acute effects of different types of cannabis on young adult and adolescent resting-state brain networks.. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 49(10), 1640-1651. https://doi.org/10.1038/s41386-024-01891-6
MLA
Ertl, Natalie, et al. "Acute effects of different types of cannabis on young adult and adolescent resting-state brain networks.." Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 2024. https://doi.org/10.1038/s41386-024-01891-6
RethinkTHC
RethinkTHC Research Database. "Acute effects of different types of cannabis on young adult ..." RTHC-05296. Retrieved from https://rethinkthc.com/research/ertl-2024-acute-effects-of-different
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.