Compared to 15 controls, 15 chronic cannabis users showed lower error-correction rates and reduced activation in brain regions responsible for processing mistakes and learning from them.
Read this if you're a regular cannabis user and have noticed difficulty learning from mistakes.
Cannabis users showed reduced dACC and hippocampal error-processing activity
What the researchers found
Fifteen chronic cannabis users and 15 controls completed a paired-associate learning task during brain scanning. The task allowed researchers to track when participants successfully learned from their mistakes versus repeating the same errors.
Cannabis users corrected fewer errors overall and showed reduced activation in two key brain regions during error processing: the dorsal anterior cingulate cortex (dACC, which monitors for mistakes) and the left hippocampus (which re-encodes correct information after an error). In controls, the dACC showed significantly different activation between corrected and repeated errors, indicating the brain was distinguishing between productive and unproductive error processing. Cannabis users did not show this distinction.
The findings suggest that chronic cannabis use impairs the brain's ability to detect mistakes and use that feedback to improve performance.
Why it matters
Learning from mistakes is fundamental to adapting behavior. This impairment in error-based learning could contribute to the difficulty cannabis-dependent individuals have in changing their behavior, including reducing or stopping use despite negative consequences.
The numbers in context
15 cannabis users vs. 15 controls. Lower error-correction rate in cannabis users. Reduced dACC and left hippocampal activation during error processing. Control group showed significant distinction between corrected and repeated errors; cannabis group did not.
How the study worked
Cross-sectional fMRI study comparing 15 chronic cannabis users (mean age 22.4) with 15 matched controls (mean age 23.3) on a paired-associate learning task that tracked error correction during brain scanning.
What this study cannot tell us
Very small sample (15 per group) limits statistical power and generalizability. Cross-sectional design cannot determine whether cannabis caused the impairments or whether pre-existing differences predisposed both cannabis use and poorer error learning. Only 4 females included.
How to read the evidence
Small cross-sectional fMRI study. Cannot determine causation. Findings need replication in larger samples.
When this study was published
Published in 2015. Error-processing research in cannabis users has continued.
The bigger picture
The inability to learn from mistakes is a hallmark of addiction more broadly. This study suggests that chronic cannabis use specifically impairs the brain circuits responsible for this type of learning, which may perpetuate continued use despite negative outcomes.
Questions still open
- Does error-learning ability recover after cannabis cessation? Are these brain differences present before cannabis use begins? Would the results hold in a larger, more diverse sample?
Common questions
Does cannabis affect your ability to learn from mistakes?
Which brain regions were affected?
Read the original research
Impaired learning from errors in cannabis users: Dorsal anterior cingulate cortex and hippocampus hypoactivity.
Drug and alcohol dependence, 155, 175-82
Citation
Carey, Susan E; Nestor, Liam; Jones, Jennifer; Garavan, Hugh; Hester, Robert. (2015). Impaired learning from errors in cannabis users: Dorsal anterior cingulate cortex and hippocampus hypoactivity.. Drug and alcohol dependence, 155, 175-82. https://doi.org/10.1016/j.drugalcdep.2015.07.671
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