THC impaired the brain's ability to stop unwanted responses, and the impairment correlated with psychotic symptoms
In 36 healthy men, THC caused more errors on a stop-signal task and reduced activation in a brain region critical for impulse control, with both effects correlating with the severity of transient psychotic symptoms.
Quick Facts
What This Study Found
Researchers gave 36 healthy men with minimal cannabis exposure either 10mg of oral THC or placebo in a double-blind crossover design, then scanned their brains during a task requiring them to withhold automatic responses (Go/No-Go task).
THC increased inhibition errors and reduced inhibition efficiency compared to placebo. It also reduced activation in the left inferior frontal gyrus, a brain region critical for stopping unwanted actions. The severity of transient psychotic symptoms induced by THC directly correlated with more frequent inhibition errors and lower inhibition efficiency.
The left inferior frontal activation was inversely correlated with both error frequency and psychotic symptom severity, suggesting that THC's disruption of this brain region may be a mechanism linking cannabis to transient psychotic experiences.
Key Numbers
36 healthy men studied in crossover design. 10mg oral THC vs. placebo. THC increased inhibition errors and reduced inhibition efficiency. Left inferior frontal activation was reduced by THC. Psychotic symptom severity correlated with error frequency.
How They Did This
Randomized, placebo-controlled, double-blind, within-subject crossover design. 36 healthy right-handed men with minimal cannabis exposure received 10mg oral delta-9-THC or placebo on separate sessions. Brain activation was measured with fMRI during a Go/No-Go response inhibition task.
Why This Research Matters
This study provides experimental evidence that THC disrupts the brain's ability to suppress unwanted responses, and that this specific cognitive impairment is directly related to the psychotic symptoms that THC can temporarily induce. This mechanistic link helps explain why cannabis use is associated with psychosis risk.
The Bigger Picture
The ability to inhibit thoughts and actions is fundamental to organized behavior. This study shows THC specifically disrupts this capacity in a brain region also implicated in schizophrenia, providing a concrete neural mechanism for how cannabis might contribute to psychotic experiences.
What This Study Doesn't Tell Us
The study used healthy men with minimal cannabis exposure, so results may not generalize to regular users who may develop tolerance. Oral THC administration differs from smoked cannabis. 10mg is a specific dose and effects may vary at other doses. The crossover design means order effects are possible.
Questions This Raises
- ?Would regular cannabis users show the same inhibitory deficits and brain changes?
- ?Does CBD counteract THC's effects on inhibitory control?
- ?Is the left inferior frontal disruption reversible with cessation?
Trust & Context
- Key Stat:
- THC-induced inhibition deficits correlated with psychotic symptom severity
- Evidence Grade:
- Randomized, placebo-controlled crossover design with brain imaging in 36 participants. Strong experimental design for a cannabis neuroscience study.
- Study Age:
- Published in 2015 using a well-controlled experimental design.
- Original Title:
- Impairment of inhibitory control processing related to acute psychotomimetic effects of cannabis.
- Published In:
- European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 25(1), 26-37 (2015)
- Authors:
- Bhattacharyya, Sagnik(39), Atakan, Z(5), Martin-Santos, R(3), Crippa, J A, Kambeitz, J, Malhi, S, Giampietro, V, Williams, S, Brammer, M, Rubia, K, Collier, D A, McGuire, P K
- Database ID:
- RTHC-00921
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Does THC cause psychosis?
This study showed that THC can temporarily induce psychotic symptoms in healthy people and that these symptoms are linked to specific impairments in inhibitory brain function. This does not mean everyone who uses THC will develop psychosis, but it reveals a neural mechanism for the association.
What is inhibitory control?
Inhibitory control is the brain's ability to suppress unwanted thoughts, impulses, and automatic responses. It is essential for goal-directed behavior and is disrupted in several psychiatric conditions, including schizophrenia.
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Cite This Study
https://rethinkthc.com/research/RTHC-00921APA
Bhattacharyya, Sagnik; Atakan, Z; Martin-Santos, R; Crippa, J A; Kambeitz, J; Malhi, S; Giampietro, V; Williams, S; Brammer, M; Rubia, K; Collier, D A; McGuire, P K. (2015). Impairment of inhibitory control processing related to acute psychotomimetic effects of cannabis.. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 25(1), 26-37. https://doi.org/10.1016/j.euroneuro.2014.11.018
MLA
Bhattacharyya, Sagnik, et al. "Impairment of inhibitory control processing related to acute psychotomimetic effects of cannabis.." European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 2015. https://doi.org/10.1016/j.euroneuro.2014.11.018
RethinkTHC
RethinkTHC Research Database. "Impairment of inhibitory control processing related to acute..." RTHC-00921. Retrieved from https://rethinkthc.com/research/bhattacharyya-2015-impairment-of-inhibitory-control
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.