Cannabis and Cocaine Had Opposite Acute Effects on Impulse Control and Brain Activity
In a controlled study, cocaine improved accuracy and speed on an impulse control task while cannabis impaired both, and their effects on brain electrical activity were mirror images of each other.
Quick Facts
What This Study Found
In a double-blind, placebo-controlled crossover study, 38 healthy drug-using volunteers received cocaine, cannabis, and placebo in separate sessions and performed a Go/NoGo impulse control task.
Cocaine improved performance: faster reaction times, better accuracy, and increased prefrontal NoGo-P3 brain activity (reflecting enhanced evaluative processing). Cannabis produced the opposite: slower reactions, worse accuracy, and decreased NoGo-P3 amplitude.
Cannabis also reduced the parietal P3 wave, suggesting broader attention disruption beyond just impulse control. Cocaine did not affect this component, indicating its effects were more specific to response control.
Neither drug affected the N2 brain wave component, which reflects the earlier, pre-motor stage of response inhibition. This means both drugs acted on the evaluative stage (deciding whether the response was appropriate) rather than the initial detection stage.
Neither trait impulsivity nor novelty seeking moderated any drug effects.
Key Numbers
38 participants in a three-way crossover design. Cocaine: faster RTs, better accuracy, increased prefrontal NoGo-P3. Cannabis: slower RTs, worse accuracy, decreased prefrontal NoGo-P3 and parietal P3. Neither drug affected N2. Personality traits did not moderate effects.
How They Did This
Double-blind, placebo-controlled, randomized three-way crossover design. 38 healthy drug-using volunteers completed a Go/NoGo task after receiving cocaine, cannabis, or placebo in separate sessions. Event-related potentials (ERPs) were recorded via EEG. Trait impulsivity and novelty seeking were measured as potential moderators.
Why This Research Matters
This is one of the few controlled studies directly comparing how two commonly used drugs affect the same cognitive process in the same individuals. The finding that they have precisely opposite effects on impulse control, and that these effects are reflected in measurable brain activity, provides a clear neural picture of how these substances modify cognitive function.
The Bigger Picture
Understanding how different drugs affect impulse control has implications for driving safety, workplace performance, and treatment. The mirror-image effects of cocaine and cannabis on the same brain process illustrate why polysubstance use creates complex and potentially unpredictable cognitive states.
What This Study Doesn't Tell Us
All participants were experienced drug users, so results may not generalize to drug-naive individuals. The study measured acute effects of single doses and does not address chronic use patterns. The crossover design controls for individual differences but cannot capture long-term neuroadaptations. Sample size was moderate.
Questions This Raises
- ?What happens to impulse control when cocaine and cannabis are used simultaneously, as they frequently are?
- ?Would these effects be more or less pronounced in non-experienced users?
- ?Do the ERP changes predict real-world impulsive behavior like risky driving?
Trust & Context
- Key Stat:
- Cannabis and cocaine had precisely opposite effects on impulse control accuracy, speed, and brain wave amplitude.
- Evidence Grade:
- Strong evidence from a well-designed double-blind, placebo-controlled, within-subject crossover study using both behavioral and neurophysiological measures.
- Study Age:
- Published in 2016. The acute cognitive effects of cannabis continue to be studied with advancing neuroimaging and EEG techniques.
- Original Title:
- Acute effects of cocaine and cannabis on response inhibition in humans: an ERP investigation.
- Published In:
- Addiction biology, 21(6), 1186-1198 (2016)
- Authors:
- Spronk, Desirée B, De Bruijn, Ellen R A(2), van Wel, Janelle H P, Ramaekers, Johannes G, Verkes, Robbert J
- Database ID:
- RTHC-01269
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 cannabis affect impulse control?
Yes. In this controlled study, cannabis acutely impaired impulse control by slowing responses, reducing accuracy, and decreasing brain activity associated with evaluating whether a response was appropriate. These effects were the opposite of those produced by cocaine.
Does personality predict how drugs affect you?
Not in this study. Neither trait impulsivity nor novelty seeking moderated how cocaine or cannabis affected impulse control, suggesting the drug effects are pharmacological rather than personality-dependent.
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Cite This Study
https://rethinkthc.com/research/RTHC-01269APA
Spronk, Desirée B; De Bruijn, Ellen R A; van Wel, Janelle H P; Ramaekers, Johannes G; Verkes, Robbert J. (2016). Acute effects of cocaine and cannabis on response inhibition in humans: an ERP investigation.. Addiction biology, 21(6), 1186-1198. https://doi.org/10.1111/adb.12274
MLA
Spronk, Desirée B, et al. "Acute effects of cocaine and cannabis on response inhibition in humans: an ERP investigation.." Addiction biology, 2016. https://doi.org/10.1111/adb.12274
RethinkTHC
RethinkTHC Research Database. "Acute effects of cocaine and cannabis on response inhibition..." RTHC-01269. Retrieved from https://rethinkthc.com/research/spronk-2016-acute-effects-of-cocaine
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.