Combining mouse experiments with human brain imaging, researchers identified specific genes and cell types that may explain how cannabis use during adolescence alters cortical thickness.
Neuroscience-minded readers, parents of teens, and researchers studying cannabis effects on brain development.
13 THC-related genes correlated with cortical thickness changes in human adolescents
What the researchers found
In mice, THC exposure caused spine loss and reduced dendritic complexity in frontal cortex pyramidal cells. In human adolescents who used cannabis before age 16 (n=140 vs 327 controls), cortical thickness differences correlated spatially with the expression of 13 THC-related genes linked to astrocytes, microglia, and a type of pyramidal cell.
Why it matters
This study bridges a major gap between animal neuroscience and human brain imaging. By linking specific genes and cell types to observable cortical thickness changes, it offers a biological mechanism for how cannabis may affect the developing adolescent brain.
The numbers in context
140 human adolescents who used cannabis before 16 vs 327 controls; 34 brain regions measured; 13 THC-related genes correlated with cortical thickness differences; 3 cell types implicated (astrocytes, microglia, pyramidal cells); 37 THC-related genes enriched in neuron projection development
How the study worked
Three-step design: (1) adolescent male mice exposed to THC or synthetic cannabinoid WIN, with gene expression and dendritic analysis in frontal cortex; (2) MRI comparison of cortical thickness in 34 brain regions between human adolescents who used cannabis before 16 and those who did not; (3) spatial correlation of human group differences with mouse-identified gene expression.
What this study cannot tell us
Mouse experiments used only male animals. The human component was observational (cannot prove causation). Cannabis use was self-reported, and the specific compounds, doses, and frequency of human cannabis use were not controlled.
How to read the evidence
Strong translational design combining animal experiments with human imaging, though the human component is observational.
When this study was published
Published in 2024.
The bigger picture
The finding that cannabis-related brain changes in humans map onto specific gene expression patterns identified in mice provides some of the strongest translational evidence to date for a biological pathway through which cannabis affects adolescent brain development.
Questions still open
- Do the same cellular mechanisms apply in female adolescents?
- Are these cortical changes reversible if cannabis use stops during adolescence?
Common questions
What did cannabis actually do to brain cells in mice?
Does this prove cannabis damages teenage brains?
Read the original research
Cells and Molecules Underpinning Cannabis-Related Variations in Cortical Thickness during Adolescence.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 44(41)
Citation
Navarri, Xavier; Robertson, Derek N; Charfi, Iness; Wünnemann, Florian; Sâmia Fernandes do Nascimento, Antônia; Trottier, Giacomo; Leclerc, Sévérine; Andelfinger, Gregor U; Di Cristo, Graziella; Richer, Louis; Pike, G Bruce; Pausova, Zdenka; Piñeyro, Graciela; Paus, Tomáš. (2024). Cells and Molecules Underpinning Cannabis-Related Variations in Cortical Thickness during Adolescence.. The Journal of neuroscience : the official journal of the Society for Neuroscience, 44(41). https://doi.org/10.1523/JNEUROSCI.2256-23.2024
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