THC Alone (Not CBD) Reduced Some Opioid Withdrawal Signs in Monkeys
In morphine-dependent rhesus monkeys, THC at 1.0 mg/kg reduced some behavioral and physiological withdrawal signs, but CBD alone or combined with THC had no effect, and THC was not more effective than the existing medication lofexidine.
Quick Facts
What This Study Found
THC at 1.0 mg/kg decreased unusual tongue movements (a key behavioral sign of opioid withdrawal in monkeys) and heart rate. Lofexidine at 0.32 mg/kg decreased tongue movements, blood pressure, heart rate, and activity. CBD alone (10-17.8 mg/kg) or combined with THC (0.32 mg/kg) had no significant effect on any withdrawal measure.
Key Numbers
THC 1.0 mg/kg: decreased tongue movements and heart rate; lofexidine 0.32 mg/kg: decreased tongue movements, blood pressure, heart rate, activity; CBD 10-17.8 mg/kg: no significant effect alone or with THC 0.32 mg/kg; 3 male rhesus monkeys; morphine 3.2 mg/kg BID
How They Did This
Three male rhesus monkeys received escalating morphine doses up to 3.2 mg/kg twice daily for at least 2 weeks. Morphine was then discontinued for 2 days while behavioral signs (tongue movements) and physiological measures (blood pressure, heart rate, temperature, activity) were assessed after THC, CBD, THC+CBD, lofexidine, or vehicle administration.
Why This Research Matters
Cannabinoids have been proposed as treatments for opioid withdrawal, but this study shows CBD did not help and THC was only modestly effective, not outperforming an already available medication. This tempers enthusiasm for cannabis-based opioid withdrawal treatments.
The Bigger Picture
The opioid crisis has driven interest in any potential treatment for withdrawal. While THC showed some benefit, it did not outperform lofexidine (an existing non-opioid medication), and CBD showed no benefit at all, suggesting cannabinoids are unlikely to be a breakthrough for opioid withdrawal management.
What This Study Doesn't Tell Us
Only 3 monkeys (very small sample), only male animals, specific dosing paradigm may not generalize, withdrawal from morphine may differ from withdrawal from other opioids, acute dosing does not address chronic treatment potential
Questions This Raises
- ?Would higher CBD doses produce effects?
- ?Does THC help with subjective withdrawal experiences not captured by these measures?
- ?Could cannabinoids serve as adjuncts rather than replacements for existing withdrawal medications?
Trust & Context
- Key Stat:
- CBD alone or with THC had no effect on opioid withdrawal signs in monkeys
- Evidence Grade:
- Very small animal study (3 monkeys) with limited generalizability; provides important negative data about CBD for opioid withdrawal
- Study Age:
- Published 2025
- Original Title:
- Effects of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and THC:CBD mixtures on behavioral and physiological signs of morphine withdrawal in rhesus monkeys.
- Published In:
- The Journal of pharmacology and experimental therapeutics, 392(9), 103671 (2025)
- Database ID:
- RTHC-06159
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Can cannabis help with opioid withdrawal?
In this monkey study, THC modestly reduced some withdrawal signs (abnormal tongue movements and elevated heart rate) but was not more effective than lofexidine, an already available non-opioid medication. CBD had no effect.
Why did CBD not help with opioid withdrawal?
Despite theoretical reasons to expect CBD might help, doses of 10-17.8 mg/kg produced no significant effects on any behavioral or physiological withdrawal measure, whether given alone or combined with THC.
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Cite This Study
https://rethinkthc.com/research/RTHC-06159APA
Carey, Lawrence M; Galbo-Thomma, Lindsey K; Maguire, David R; France, Charles P. (2025). Effects of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and THC:CBD mixtures on behavioral and physiological signs of morphine withdrawal in rhesus monkeys.. The Journal of pharmacology and experimental therapeutics, 392(9), 103671. https://doi.org/10.1016/j.jpet.2025.103671
MLA
Carey, Lawrence M, et al. "Effects of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and THC:CBD mixtures on behavioral and physiological signs of morphine withdrawal in rhesus monkeys.." The Journal of pharmacology and experimental therapeutics, 2025. https://doi.org/10.1016/j.jpet.2025.103671
RethinkTHC
RethinkTHC Research Database. "Effects of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD),..." RTHC-06159. Retrieved from https://rethinkthc.com/research/carey-2025-effects-of-9tetrahydrocannabinol-thc
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.