Weed or Wheel! fMRI, Behavioural, and Toxicological Investigations of How Cannabis Smoking Affects Skills Necessary for Driving
Giovanni Battistella, E. Fornari, A. Thomas, J. Mall, H. Chtioui, Monique Appenzeller, J. Annoni, Bernard Favrat, P. Maeder, Christian Giroud
PLoS One January 2, 2013 DOI: 10.1371/journal.pone.0052545 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Randomized, placebo-controlled crossover fMRI study Peer reviewed |
|---|---|
| Sample size | 31 |
| Population | Male occasional cannabis smokers |
| Intervention | Placebo |
| Topics | Cannabis |
| Key points | Cannabis smoking, even at low blood THC concentrations, decreased psychomotor tracking performance and altered activity in brain networks for salience detection and executive control compared with placebo. The changes correlated with subjective confusion rather than blood THC level, which the authors say supports zero-tolerance drugged-driving policies. |
Abstract
Marijuana is the most widely used illicit drug, however its effects on cognitive functions underling safe driving remain mostly unexplored. Our goal was to evaluate the impact of cannabis on the driving ability of occasional smokers, by investigating changes in the brain network involved in a tracking task. The subject characteristics, the percentage of Δ9-Tetrahydrocannabinol in the joint, and the inhaled dose were in accordance with real-life conditions. Thirty-one male volunteers were enrolled in this study that includes clinical and toxicological aspects together with functional magnetic resonance imaging of the brain and measurements of psychomotor skills. The fMRI paradigm was based on a visuo-motor tracking task, alternating active tracking blocks with passive tracking viewing and rest condition. We show that cannabis smoking, even at low Δ9-Tetrahydrocannabinol blood concentrations, decreases psychomotor skills and alters the activity of the brain networks involved in cognition. The relative decrease of Blood Oxygen Level Dependent response (BOLD) after cannabis smoking in the anterior insula, dorsomedial thalamus, and striatum compared to placebo smoking suggests an alteration of the network involved in saliency detection. In addition, the decrease of BOLD response in the right superior parietal cortex and in the dorsolateral prefrontal cortex indicates the involvement of the Control Executive network known to operate once the saliencies are identified. Furthermore, cannabis increases activity in the rostral anterior cingulate cortex and ventromedial prefrontal cortices, suggesting an increase in self-oriented mental activity. Subjects are more attracted by intrapersonal stimuli (“self”) and fail to attend to task performance, leading to an insufficient allocation of task-oriented resources and to sub-optimal performance. These effects correlate with the subjective feeling of confusion rather than with the blood level of Δ9-Tetrahydrocannabinol. These findings bolster the zero-tolerance policy adopted in several countries that prohibits the presence of any amount of drugs in blood while driving.
Comparable studies
Other randomized controlled trials on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment Healthy participants | 2012 | Randomized controlled trial | n = 48 |
| Distinct Effects of Δ9-Tetrahydrocannabinol and Cannabidiol on Neural Activation During Emotional Processing Healthy, English-native, right-handed men who had used cannabis 15 times or less in... | 2009 | Double-blind, randomized, placebo-controlled crossover trial | n = 15 |
| Acute Effects of a Single, Oral dose of d9-tetrahydrocannabinol (THC) and Cannabidiol (CBD) Administration in Healthy Volunteers Healthy male subjects | 2012 | Randomized controlled trial | n = 16 |
| Modulation of Mediotemporal and Ventrostriatal Function in Humans by Δ9-Tetrahydrocannabinol Healthy, native English-speaking, right-handed men of white race/ethnicity who had used... | 2009 | Randomized controlled trial | n = 15 |
| Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition Healthy volunteers with a history of light cannabis use | 2019 | Randomized, double-blind, within-subjects crossover | n = 14 |
Citations in the library
Cited by 11
- Functional brain connectomes reflect acute and chronic cannabis use Scientific Reports February 14, 2022
- Psychedelic symptoms of cannabis and cocaine use as a function of trait impulsivity Journal of Psychopharmacology January 8, 2015
- Cannabis Perturbs Dynamic Brain States Biological Psychiatry October 21, 2025
- Task-independent acute effects of delta-9-tetrahydrocannabinol on human brain function and its relationship with cannabinoid receptor gene expression: a neuroimaging meta-regression analysis bioRxiv (Cold Spring Harbor Laboratory) November 3, 2021
- The subjective effects of △9-tetrahydrocannabinol: A systematic review and dose-response meta-regression. Neuroscience & Biobehavioral Reviews June 3, 2026
and 6 more in the library
Cites 11
- A default mode of brain function Proceedings of the National Academy of Sciences January 16, 2001
- Neuroimaging in cannabis use: a systematic review of the literature Psychological Medicine July 23, 2009
- The Circumplex Structure of Depersonalization/Derealization International Journal of Psychological Studies November 21, 2010
- Structural MRI findings in long-term cannabis users: what do we know? Substance Use & Misuse September 2010
- Neurocognitive performance during acute THC intoxication in heavy and occasional cannabis users. Journal of Psychopharmacology May 2009
and 6 more in the library