What topics does this cannabis study cover?

This study covers research on: THC, Pain.

Where was this research published?

Published in European journal of pain (London, England) on May 1, 2026.

THC shows no withdrawal symptoms in pain patients, new study reveals

Q: What did this research study find?

This study examined how repeated *THC* injections affect rats experiencing **inflammatory pain**, comparing their responses to pain-free animals. Researchers induced inflammatory pain in male and female rats, then gave them twice-daily *THC* injections for a week. While the injections did reduce phy

Repeated Tetrahydrocannabinol Injections Induce Tolerance but Do Not Disrupt Ongoing Behaviour Upon Withdrawal in Male and Female Rats With Inflammatory Pain.

European journal of pain (London, England) • May 1, 2026 • Moderately Relevant

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AI Summary

This study examined how repeated THC injections affect rats experiencing inflammatory pain, comparing their responses to pain-free animals. Researchers induced inflammatory pain in male and female rats, then gave them twice-daily THC injections for a week. While the injections did reduce physical activity in both sexes, male rats developed tolerance faster than females. Importantly, when the THC injections stopped, the researchers found no evidence of withdrawal symptoms in either group—no behavioral changes, irritability, or other signs typically associated with drug dependence, despite 6 days of continuous monitoring.

The findings challenge common assumptions about THC and physical dependence, particularly in the context of pain management. Unlike opioids (such as morphine), which show enhanced withdrawal symptoms when combined with pain, repeated THC use did not trigger withdrawal, whether animals were experiencing pain or not. This suggests that while tolerance to THC's effects develops with repeated use, physical dependence is not a significant concern for pain patients using cannabis. The study notes that any limitations on THC as a pain treatment stem primarily from side effects and tolerance development rather than addiction-related withdrawal—an important distinction for patients considering cannabis-based pain management.

The research also revealed interesting sex differences in how the body responds to THC, with males showing more pronounced tolerance development. This finding underscores the importance of studying both sexes in cannabis research, as pain management strategies may need to be personalized based on biological sex for optimal therapeutic outcomes.

📄 Original Abstract

Many people use cannabis to self-medicate for pain. Little is known about the impact of pain on tolerance and spontaneous withdrawal to delta-9-tetrahydrocannabinal (THC), the primary psychoactive compound in cannabis. Our previous research with the opioid morphine suggests persistent pain will increase the magnitude and duration of THC withdrawal. Male and female Sprague-Dawley rats were individually housed in a cage with a running wheel to provide a continuous and objective measure of well-being. All rats were injected with Complete Freund's Adjuvant (CFA) into the right hindpaw to induce inflammatory pain. Beginning 1 day later, rats received twice daily THC or vehicle injections for 7 days followed by assessment of tolerance and spontaneous withdrawal. Administration of CFA decreased wheel running. Twice daily injections of THC (3 mg/kg/injection) caused a further reduction in running in male and female rats. Tolerance to the THC-induced decrease in running was more pronounced in male compared to female rats. There was no evidence of spontaneous withdrawal to THC despite continuous assessment for 6 days. Likewise, withdrawal had no effect on body weight. The lack of spontaneous withdrawal in rats with hindpaw inflammation is consistent with our recent study showing a lack of spontaneous withdrawal to THC in pain free rats, but opposite to our opioid research showing enhancement of spontaneous withdrawal to morphine in rats with hindpaw inflammation. In sum, persistent inflammatory pain does not appear to alter the effects of repeated THC injections in male or female rats. The use of THC as a treatment for pain is limited by side effects and tolerance but not by dependence associated withdrawal symptoms.

Paper Type

📄 Research

Publication

Journal: European journal of pain (London, England)
Published: May 1, 2026
PMID: 42028989
DOI: 10.1002/ejp.70279

Authors (2)

Michael M Morgan Washington State University Vancouver, Vancouver, Washington, USA.
Christa M Hickey Washington State University Vancouver, Vancouver, Washington, USA.