In an fMRI study of 87 adolescents, increasing cannabis use disorder severity was associated with decreased brain activation in the amygdala, frontal cortex, and fusiform gyrus when viewing looming threats, while alcohol use disorder showed no such association.
Adolescent psychiatrists, neuroscientists studying cannabis effects on the developing brain, and parents concerned about teen cannabis use.
Dulled amygdala threat response
What the researchers found
Increasing CUD symptomatology was associated with decreased responding to looming threat stimuli in regions including rostral frontal cortex, fusiform gyrus, and amygdala. This pattern was specific to cannabis use disorder; alcohol use disorder severity showed no relationship with threat responsiveness.
Why it matters
Dulled threat responsiveness could have real-world consequences for adolescent safety and decision-making. The finding that this effect is specific to cannabis and not alcohol suggests a unique neurotoxic impact of cannabis on the developing threat processing system.
The numbers in context
87 adolescents scanned. 45 above clinical cutoffs for CUD or AUD. Decreased activation in amygdala, rostral frontal cortex, and fusiform gyrus with increasing CUD severity. No relationship with AUD severity.
How the study worked
fMRI study of 87 adolescents (43 male) with varying CUD/AUD severity (45 above clinical cutoffs). Scanned during a looming threat task with threatening and neutral faces/animals that appeared to approach or recede.
What this study cannot tell us
Cross-sectional design cannot determine whether CUD caused the brain changes or whether pre-existing differences predispose to CUD. Relatively small sample. CUD and AUD severity were correlated, though the study controlled for this. Cannabis is not the only factor affecting these brain regions in adolescence.
How to read the evidence
Rated moderate because this is a well-designed neuroimaging study with clinical relevance, though the cross-sectional design limits causal inference.
When this study was published
Published in 2019.
The bigger picture
The amygdala and frontal cortex are critical for detecting and responding to danger. If adolescent cannabis use blunts these responses, it could affect risk assessment, social judgment, and emotional processing in ways that compound other known effects of cannabis on the developing brain.
Questions still open
- Does threat response recover with cannabis abstinence? Do these brain changes predict real-world risk-taking behavior? Is there a critical period during which adolescent cannabis exposure most affects threat processing?
Common questions
Does teen cannabis use affect how the brain responds to threats?
Is this effect specific to cannabis?
Read the original research
Threat Responsiveness as a Function of Cannabis and Alcohol Use Disorder Severity.
Journal of child and adolescent psychopharmacology, 29(7), 526-534
Citation
Blair, Robert James R; White, Stuart F; Tyler, Patrick M; Johnson, Kimberly; Lukoff, Jennie; Thornton, Laura C; Leiker, Emily K; Filbey, Francesca; Dobbertin, Matt; Blair, Karina S. (2019). Threat Responsiveness as a Function of Cannabis and Alcohol Use Disorder Severity.. Journal of child and adolescent psychopharmacology, 29(7), 526-534. https://doi.org/10.1089/cap.2019.0004
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