High-Dose Cannabis Disrupts the Brain's Error Detection System
A high dose of vaporized cannabis (22mg THC) significantly reduced the brain's automatic error detection signal in frequent users, while even a low dose (5.5mg THC) impaired conscious error recognition.
Quick Facts
What This Study Found
Researchers used EEG to measure two brain signals related to error monitoring in frequent cannabis users: the error-related negativity (ERN), which reflects automatic error detection, and the error positivity (Pe), which reflects conscious error awareness.
Participants who received a high dose (22mg THC) showed significantly reduced ERN compared to placebo, meaning their brains were less effective at automatically detecting mistakes. Both high and low doses (5.5mg THC) reduced the Pe signal, suggesting that even modest cannabis doses impair conscious recognition of errors.
These effects occurred in people who already used cannabis at least four times per week, indicating that regular use does not fully protect against acute impairment of error monitoring.
Key Numbers
55 frequent cannabis users; 3 groups (placebo n=19, low dose n=18, high dose n=18); high dose significantly reduced ERN; both doses significantly reduced Pe vs. placebo
How They Did This
Randomized, double-blind, between-groups design. Frequent cannabis users (minimum 4 times/week for 2+ years) were assigned to receive placebo (n=19), low-dose 5.5mg THC (n=18), or high-dose 22mg THC (n=18) via vaporizer. Error monitoring was measured using EEG during a Flanker task.
Why This Research Matters
Error monitoring is essential for recognizing and correcting mistakes in real time. Impairment of this process could affect driving, work performance, and decision-making, even in people who use cannabis regularly and may believe they have developed tolerance.
The Bigger Picture
This dose-response pattern suggests that cannabis impairs error awareness at low doses and disrupts deeper automatic error detection at higher doses. For frequent users who believe tolerance protects them from cognitive effects, this finding is particularly relevant.
What This Study Doesn't Tell Us
Between-groups design means individual differences could influence results. Relatively small groups (18-19 per condition). Only examined frequent users, so results may not generalize to occasional users. Acute effects may not reflect chronic patterns.
Questions This Raises
- ?Does impaired error monitoring during cannabis intoxication contribute to real-world accidents?
- ?Do these effects persist after the acute high wears off?
- ?Would different cannabinoid ratios (e.g., CBD-dominant) show the same pattern?
Trust & Context
- Key Stat:
- Even low-dose THC (5.5mg) impaired conscious error recognition
- Evidence Grade:
- Well-designed RCT with objective EEG measures, but small sample sizes per group and between-groups design limit statistical power.
- Study Age:
- Published in 2015. Cannabis potency has increased substantially since this study.
- Original Title:
- Dose-dependent effects of cannabis on the neural correlates of error monitoring in frequent cannabis users.
- Published In:
- European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 25(11), 1943-53 (2015)
- Authors:
- Kowal, Mikael A(4), van Steenbergen, Henk(2), Colzato, Lorenza S(2), Hazekamp, Arno, van der Wee, Nic J A, Manai, Meriem, Durieux, Jeffrey, Hommel, Bernhard
- Database ID:
- RTHC-00994
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
What is error monitoring?
It is the brain's ability to detect and respond to mistakes. It involves both an automatic process (catching errors immediately) and a conscious process (becoming aware of the error). Cannabis appears to impair both.
Does tolerance protect regular users from this effect?
Not fully. These participants used cannabis at least four times per week for at least two years, yet still showed significant impairment in error monitoring when given THC.
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
- does-weed-expire-shelf-life-potency
- how-to-store-weed-fresh-temperature-light
- what-is-dabbing-what-does-it-do-body
- what-are-moon-rocks-why-strong
Cite This Study
https://rethinkthc.com/research/RTHC-00994APA
Kowal, Mikael A; van Steenbergen, Henk; Colzato, Lorenza S; Hazekamp, Arno; van der Wee, Nic J A; Manai, Meriem; Durieux, Jeffrey; Hommel, Bernhard. (2015). Dose-dependent effects of cannabis on the neural correlates of error monitoring in frequent cannabis users.. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 25(11), 1943-53. https://doi.org/10.1016/j.euroneuro.2015.08.001
MLA
Kowal, Mikael A, et al. "Dose-dependent effects of cannabis on the neural correlates of error monitoring in frequent cannabis users.." European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 2015. https://doi.org/10.1016/j.euroneuro.2015.08.001
RethinkTHC
RethinkTHC Research Database. "Dose-dependent effects of cannabis on the neural correlates ..." RTHC-00994. Retrieved from https://rethinkthc.com/research/kowal-2015-dosedependent-effects-of-cannabis
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.