Adolescent cannabis users performed worse on impulse control tasks and showed unusual connectivity between brain regions involved in response inhibition, even during rest.
Read this if you want to understand how adolescent cannabis use may affect brain wiring involved in impulse control.
Abnormal brain connectivity correlated with recent cannabis use, visible even at rest
What the researchers found
Adolescent heavy cannabis users and matched non-using controls completed a Go/No-Go task (requiring them to inhibit a habitual response) during brain imaging. Cannabis users made more errors on the task, indicating poorer impulse control.
Surprisingly, when researchers looked at which brain regions activated during the task, there were no differences between groups. Instead, the difference appeared in how brain regions communicated with each other: cannabis users showed heightened correlation patterns between bilateral inferior parietal lobules and the left cerebellum.
This abnormal connectivity pattern was replicated using resting-state brain imaging data (when participants were not performing any task) and was positively correlated with self-reported recent cannabis use. The findings suggest the problem was not in the activation of individual brain regions but in the wiring between them.
Why it matters
Most brain imaging studies of cannabis focus on which regions activate more or less. This study shifted focus to how regions connect, revealing that the problem in adolescent cannabis users may be in the communication between brain areas rather than the function of any single area.
The numbers in context
Cannabis users showed impaired Go/No-Go performance. Heightened correlation between bilateral inferior parietal lobules and left cerebellum was found during both task and rest. The connectivity pattern correlated with recent cannabis use.
How the study worked
Cross-sectional study comparing adolescent heavy cannabis users to age-matched non-using controls using a Go/No-Go paradigm during fMRI. Both task-related activation and functional connectivity were analyzed. Resting-state fMRI was also collected to assess intrinsic connectivity patterns.
What this study cannot tell us
Cross-sectional design cannot determine whether cannabis caused the connectivity changes or whether pre-existing brain differences led to cannabis use. Sample size was not reported in the abstract. The study used a synthetic measure of recent use rather than controlled dosing.
How to read the evidence
Brain imaging study with both task and resting-state replication, though cross-sectional design limits causal interpretation.
When this study was published
Published in 2014.
The bigger picture
Impulse control is critical during adolescence, a period when the brain is still developing its regulatory circuits. Finding that cannabis use is associated with disrupted connectivity in the impulse control network, observable even at rest, suggests potentially lasting effects on how the adolescent brain organizes its control systems.
Questions still open
- Do these connectivity changes normalize with sustained abstinence? Are they present before cannabis use begins, potentially predisposing some adolescents to use? Does the parietal-cerebellar connectivity pattern predict future substance use problems?
Common questions
How does cannabis affect adolescent brain connectivity?
Does cannabis use cause poor impulse control in teenagers?
Read the original research
Response inhibition and elevated parietal-cerebellar correlations in chronic adolescent cannabis users.
Neuropharmacology, 84, 131-7
Citation
Behan, B; Connolly, C G; Datwani, S; Doucet, M; Ivanovic, J; Morioka, R; Stone, A; Watts, R; Smyth, B; Garavan, H. (2014). Response inhibition and elevated parietal-cerebellar correlations in chronic adolescent cannabis users.. Neuropharmacology, 84, 131-7. https://doi.org/10.1016/j.neuropharm.2013.05.027
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