Brain Differences Linked to Cannabis Use Actually Existed Before Teens Ever Tried Cannabis
A prospective neuroimaging study found that brain activation differences and poorer executive function existed at age 12 - before any cannabis use - in teens who would go on to initiate cannabis by age 15, supporting a risk model over a cannabis-caused damage model.
Quick Facts
What This Study Found
At age 12, before any cannabis use, teens who would initiate cannabis by 15 already showed activation differences in frontoparietal (increased) and visual association (decreased) regions, and poorer executive planning scores. At follow-up, a cannabis dose-response relationship was found in cuneus activation, but this was not associated with cognitive performance. Limited support for a direct cannabis exposure effect.
Key Numbers
85 participants, 22 initiated cannabis by age 15. Baseline (age 12) differences found in frontoparietal and visual association activation and Stockings of Cambridge executive planning scores before any cannabis use.
How They Did This
85 participants completed working memory fMRI and cognitive assessments at age 12 (before cannabis use) and age 15. By follow-up, 22 had initiated cannabis. Baseline neurocognitive measures were compared between future initiators and non-initiators.
Why This Research Matters
This is one of the strongest designs for disentangling cause and effect in cannabis neuroscience. By measuring brains before anyone used cannabis, researchers could show that many "cannabis effects" actually preceded cannabis use, fundamentally challenging the assumption that cannabis causes these brain differences.
The Bigger Picture
Many retrospective studies have attributed brain differences in cannabis users to drug effects. This prospective study shows the same differences exist before use begins, suggesting they reflect pre-existing vulnerability to substance use rather than drug-induced damage. This has major implications for how we interpret cannabis brain research.
What This Study Doesn't Tell Us
Relatively small cannabis-initiating group (n=22). Only 3 years between baseline and follow-up. More prolonged exposure may be needed to observe true cannabis effects. Cannot fully rule out other substance use effects.
Questions This Raises
- ?Do the pre-existing brain differences represent a general substance use vulnerability or something specific to cannabis?
- ?Would longer follow-up reveal true cannabis exposure effects?
- ?Could these baseline measures be used to identify at-risk youth before they begin using?
Trust & Context
- Key Stat:
- Brain activation differences and poorer executive function were already present at age 12 in teens who would initiate cannabis by 15 - before they ever used.
- Evidence Grade:
- Strong - prospective design with pre-cannabis baseline measurements is the gold standard for this research question.
- Study Age:
- Published in 2018.
- Original Title:
- Early Cannabis Use and Neurocognitive Risk: A Prospective Functional Neuroimaging Study.
- Published In:
- Biological psychiatry. Cognitive neuroscience and neuroimaging, 3(8), 713-725 (2018)
- Authors:
- Tervo-Clemmens, Brenden(3), Simmonds, Daniel(2), Calabro, Finnegan J(2), Montez, David F, Lekht, Julia A, Day, Nancy L, Richardson, Gale A, Luna, Beatriz
- Database ID:
- RTHC-01854
Evidence Hierarchy
Enrolls participants and follows them forward in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis cause brain changes in teens?
This study challenges that assumption. Brain activation differences and poorer executive function existed at age 12 - before any cannabis use - in teens who would later initiate cannabis. This suggests the differences may reflect pre-existing vulnerability rather than drug-caused damage.
Are brain differences in cannabis users caused by cannabis?
Not necessarily. This prospective study found that many brain differences previously attributed to cannabis were already present before teens ever tried the drug. The authors conclude that "the purported neurocognitive effects of early cannabis onset may not be due to cannabis initiation alone."
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-01854APA
Tervo-Clemmens, Brenden; Simmonds, Daniel; Calabro, Finnegan J; Montez, David F; Lekht, Julia A; Day, Nancy L; Richardson, Gale A; Luna, Beatriz. (2018). Early Cannabis Use and Neurocognitive Risk: A Prospective Functional Neuroimaging Study.. Biological psychiatry. Cognitive neuroscience and neuroimaging, 3(8), 713-725. https://doi.org/10.1016/j.bpsc.2018.05.004
MLA
Tervo-Clemmens, Brenden, et al. "Early Cannabis Use and Neurocognitive Risk: A Prospective Functional Neuroimaging Study.." Biological psychiatry. Cognitive neuroscience and neuroimaging, 2018. https://doi.org/10.1016/j.bpsc.2018.05.004
RethinkTHC
RethinkTHC Research Database. "Early Cannabis Use and Neurocognitive Risk: A Prospective Fu..." RTHC-01854. Retrieved from https://rethinkthc.com/research/tervo-clemmens-2018-early-cannabis-use-and
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.