Brain scans reveal different patterns of altered function in adult versus adolescent cannabis users
A meta-analysis of 20 fMRI studies found that adult cannabis users showed increased activation in temporal and frontal brain regions with decreased activation in visual and insular areas, while adolescent users showed a different pattern of changes.
Quick Facts
What This Study Found
Researchers conducted separate meta-analyses of fMRI studies comparing brain function in adult and adolescent cannabis users to non-users during various cognitive tasks.
In adult cannabis users (530 users vs 580 controls across 13 studies), brain activation was increased in the superior and posterior temporal regions and inferior frontal gyrus, while decreased in the visual cortex, insula, and middle temporal gyrus. These changes may reflect compensatory neuroadaptive processes where the brain recruits additional regions to maintain cognitive performance.
In adolescent cannabis users (219 users vs 224 controls across 7 studies), the pattern was different: increased activation was found in the inferior parietal gyrus and putamen compared to controls. The distinct patterns between age groups suggest that cannabis affects developing and mature brains through different mechanisms.
The meta-analytic approach was important because individual fMRI studies of cannabis have produced inconsistent results, making it difficult to draw conclusions from any single study.
Key Numbers
20 studies included: 13 adult, 7 adolescent. Adults: 530 cannabis users vs 580 controls. Adolescents: 219 cannabis users vs 224 controls. Adult changes: increased temporal/frontal activation, decreased visual/insular activation. Adolescent changes: increased parietal/putamen activation.
How They Did This
Systematic literature search identified 20 manuscripts (13 adult, 7 adolescent studies) meeting inclusion criteria. Separate meta-analyses used coordinate-based methods to synthesize fMRI activation data across studies employing various cognitive tasks. Adult analyses: 530 cannabis users vs 580 controls. Adolescent analyses: 219 cannabis users vs 224 controls.
Why This Research Matters
By pooling data across many studies, this meta-analysis resolves inconsistencies in individual brain imaging studies of cannabis effects. The finding that adults and adolescents show different patterns of altered brain function supports the argument that the developing brain responds differently to cannabis, with potentially different long-term consequences.
The Bigger Picture
This meta-analysis provides a clearer picture of what cannabis does to brain function than any individual study can offer. The age-dependent patterns add to growing evidence that adolescent cannabis exposure has distinct neurobiological consequences, supporting policies that aim to delay the onset of cannabis use.
What This Study Doesn't Tell Us
The studies included used different cognitive tasks, which complicates interpretation of pooled results. The meta-analysis cannot determine whether brain changes preceded or followed cannabis use. Cross-sectional data cannot assess whether changes are reversible. The adolescent analysis had fewer studies and participants than the adult analysis.
Questions This Raises
- ?Do the compensatory brain activation patterns in adult users normalize after cessation?
- ?Why does the adolescent brain show different activation changes than the adult brain?
- ?Are the functional changes associated with measurable cognitive impairment?
Trust & Context
- Key Stat:
- Different brain activation patterns in adult versus adolescent cannabis users across 20 fMRI studies
- Evidence Grade:
- This is a meta-analysis of neuroimaging studies, providing strong synthesized evidence from 20 individual studies.
- Study Age:
- Published in 2018. Neuroimaging meta-analyses of cannabis effects continue to be updated as more studies accumulate.
- Original Title:
- Residual effects of cannabis use in adolescent and adult brains - A meta-analysis of fMRI studies.
- Published In:
- Neuroscience and biobehavioral reviews, 88, 26-41 (2018)
- Authors:
- Blest-Hopley, Grace(10), Giampietro, Vincent(14), Bhattacharyya, Sagnik(39)
- Database ID:
- RTHC-01596
Evidence Hierarchy
Combines results from multiple studies to find an overall pattern.
What do these levels mean? →Frequently Asked Questions
Does cannabis change how the brain works?
Yes, according to this meta-analysis of 20 brain imaging studies. Regular cannabis users showed altered activation patterns during cognitive tasks, with increased activity in some brain regions and decreased activity in others, suggesting the brain adapts to compensate for cannabis effects.
Is the effect different for teenagers?
Yes. Adult and adolescent cannabis users showed different patterns of brain function changes. Adolescent users showed increased activation in different regions (parietal/putamen) than adults (temporal/frontal), suggesting the developing brain responds differently to cannabis.
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Cite This Study
https://rethinkthc.com/research/RTHC-01596APA
Blest-Hopley, Grace; Giampietro, Vincent; Bhattacharyya, Sagnik. (2018). Residual effects of cannabis use in adolescent and adult brains - A meta-analysis of fMRI studies.. Neuroscience and biobehavioral reviews, 88, 26-41. https://doi.org/10.1016/j.neubiorev.2018.03.008
MLA
Blest-Hopley, Grace, et al. "Residual effects of cannabis use in adolescent and adult brains - A meta-analysis of fMRI studies.." Neuroscience and biobehavioral reviews, 2018. https://doi.org/10.1016/j.neubiorev.2018.03.008
RethinkTHC
RethinkTHC Research Database. "Residual effects of cannabis use in adolescent and adult bra..." RTHC-01596. Retrieved from https://rethinkthc.com/research/blest-hopley-2018-residual-effects-of-cannabis
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.