Adding cannabis to cocaine use made cognitive problems worse, not better
Cocaine users who also used cannabis heavily performed worse on processing speed, inhibitory control, and sustained attention compared to cocaine-only users, and cannabis did not reduce cocaine relapse rates over six months.
Quick Facts
What This Study Found
Both cocaine groups performed worse than controls on multiple cognitive measures. The cocaine + cannabis group performed worse than the cocaine-only group on processing speed, inhibitory control, and sustained attention, while the cocaine-only group did worse on mental flexibility. Cannabis use did not reduce cocaine relapse at 1, 3, or 6 months.
Key Numbers
63 cocaine + cannabis users, 24 cocaine-only users, 36 controls. Follow-up at 1, 3, and 6 months. Cannabis did not decrease relapse rates at any time point.
How They Did This
Compared 63 cocaine users with heavy cannabis use, 24 cocaine users with minimal cannabis use, and 36 controls. Neurocognitive testing occurred after two weeks of supervised detoxification, with relapse follow-up at 1, 3, and 6 months.
Why This Research Matters
Some non-controlled studies have suggested smoked cannabis might help cocaine addiction. This study found the opposite: adding cannabis worsened cognitive outcomes without reducing relapse.
The Bigger Picture
The idea of using one drug to treat addiction to another is appealing but risky. This study adds to the evidence that smoked cannabis is not a safe substitute therapy for cocaine dependence.
What This Study Doesn't Tell Us
The cocaine + cannabis group was larger than the cocaine-only group, which may affect statistical power. Cannabis use was defined by a lifetime threshold (50 uses), not current frequency. This was not a randomized trial.
Questions This Raises
- ?Would CBD alone (without THC) produce different cognitive or relapse outcomes?
- ?Does the timing and dose of cannabis use relative to cocaine use matter?
Trust & Context
- Key Stat:
- Cannabis did not reduce cocaine relapse at any time point
- Evidence Grade:
- Moderate: prospective cohort with 6-month follow-up and appropriate control group, but not randomized.
- Study Age:
- Published in 2019.
- Original Title:
- Distinct effects of cocaine and cocaine + cannabis on neurocognitive functioning and abstinence: A six-month follow-up study.
- Published In:
- Drug and alcohol dependence, 205, 107642 (2019)
- Authors:
- Oliveira, Hercílio Pereira de, Gonçalves, Priscila Dib(3), Ometto, Mariella, Santos, Bernardo Dos, Malbergier, André, Amaral, Ricardo, Nicastri, Sergio, Andrade, Arthur Guerra de, Cunha, Paulo Jannuzzi
- Database ID:
- RTHC-02210
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Were people saying cannabis could treat cocaine addiction?
Some non-controlled studies and anecdotal reports suggested smoked cannabis might help cocaine users reduce use. This study tested that claim with cognitive and relapse data and did not find support.
Did cannabis help with any aspect of cocaine recovery?
The cocaine + cannabis group performed better on mental flexibility, but worse on three other cognitive measures, and cannabis did not reduce relapse rates.
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Cite This Study
https://rethinkthc.com/research/RTHC-02210APA
Oliveira, Hercílio Pereira de; Gonçalves, Priscila Dib; Ometto, Mariella; Santos, Bernardo Dos; Malbergier, André; Amaral, Ricardo; Nicastri, Sergio; Andrade, Arthur Guerra de; Cunha, Paulo Jannuzzi. (2019). Distinct effects of cocaine and cocaine + cannabis on neurocognitive functioning and abstinence: A six-month follow-up study.. Drug and alcohol dependence, 205, 107642. https://doi.org/10.1016/j.drugalcdep.2019.107642
MLA
Oliveira, Hercílio Pereira de, et al. "Distinct effects of cocaine and cocaine + cannabis on neurocognitive functioning and abstinence: A six-month follow-up study.." Drug and alcohol dependence, 2019. https://doi.org/10.1016/j.drugalcdep.2019.107642
RethinkTHC
RethinkTHC Research Database. "Distinct effects of cocaine and cocaine + cannabis on neuroc..." RTHC-02210. Retrieved from https://rethinkthc.com/research/oliveira-2019-distinct-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.