Chronic cannabis users had reduced brain activity when learning from mistakes and corrected fewer errors
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.
Quick Facts
What This Study 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.
Key Numbers
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 They Did This
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.
Why This Research 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 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.
What This Study Doesn't 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.
Questions This Raises
- ?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?
Trust & Context
- Key Stat:
- Cannabis users showed reduced dACC and hippocampal error-processing activity
- Evidence Grade:
- Small cross-sectional fMRI study. Cannot determine causation. Findings need replication in larger samples.
- Study Age:
- Published in 2015. Error-processing research in cannabis users has continued.
- Original Title:
- Impaired learning from errors in cannabis users: Dorsal anterior cingulate cortex and hippocampus hypoactivity.
- Published In:
- Drug and alcohol dependence, 155, 175-82 (2015)
- Authors:
- Carey, Susan E, Nestor, Liam(5), Jones, Jennifer, Garavan, Hugh, Hester, Robert
- Database ID:
- RTHC-00932
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does cannabis affect your ability to learn from mistakes?
In this small study, chronic cannabis users corrected fewer errors on a learning task and showed reduced brain activity in regions that process mistakes. However, the study cannot determine whether cannabis caused these differences.
Which brain regions were affected?
The dorsal anterior cingulate cortex (which monitors for errors) and the left hippocampus (which helps encode corrected information) both showed reduced activation in cannabis users during error processing.
Read More on RethinkTHC
- THC-amygdala-anxiety-brain
- anandamide-weed-withdrawal
- cannabinoid-receptors-recovery-time
- cannabis-developing-brain-teenagers
- cant-enjoy-anything-without-weed
- dopamine-recovery-after-quitting-weed
- endocannabinoid-system-explained-simply
- endocannabinoid-system-withdrawal
- nervous-system-weed-withdrawal-fight-flight
- teen-weed-use-under-18-effects-brain
- thc-brain-withdrawal
- thc-prefrontal-cortex-brain-effects
- weed-cortisol-stress-hormones
- weed-memory-loss-recovery
- weed-motivation-amotivational-syndrome
- weed-nervous-system-effects
- weed-reward-system-brain
Cite This Study
https://rethinkthc.com/research/RTHC-00932APA
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
MLA
Carey, Susan E, et al. "Impaired learning from errors in cannabis users: Dorsal anterior cingulate cortex and hippocampus hypoactivity.." Drug and alcohol dependence, 2015. https://doi.org/10.1016/j.drugalcdep.2015.07.671
RethinkTHC
RethinkTHC Research Database. "Impaired learning from errors in cannabis users: Dorsal ante..." RTHC-00932. Retrieved from https://rethinkthc.com/research/carey-2015-impaired-learning-from-errors
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.