A Rat Study’s Null Wheel-Running Result Does Not Rule Out Human Cannabis Withdrawal
Stopping repeated THC did not significantly change wheel running or body weight in a rat experiment with inflammatory pain. That is a negative finding on selected animal endpoints, not evidence that human cannabis withdrawal does not occur.
A pain model with repeated injected THC
Researchers studied 32 adult Sprague–Dawley rats, equally divided by sex. Hindpaw inflammation was induced before twice-daily subcutaneous THC at 3 mg/kg per injection or vehicle for seven days. Running wheels continuously recorded activity in the home cage.
All rats then received a THC challenge to assess tolerance. Withdrawal observations followed that challenge, with the reported withdrawal comparisons covering subsequent days. This sequence differs from simply stopping a patient’s usual oral or inhaled cannabis product.
Tolerance and withdrawal answered different questions
THC reduced running during treatment. At the challenge, previously THC-treated rats showed less suppression than rats receiving THC for the first time, supporting tolerance to that behavioral effect. Male rats showed greater tolerance than females under these conditions; the tolerance test used six females per group rather than the original eight.
During withdrawal observation, prior THC treatment was not significantly associated with dark-phase running, light-phase running, maximum speed or body weight. Those null comparisons should be preserved rather than replaced with a claim of a demonstrated withdrawal deficit.
Why the negative finding has boundaries
The measured outcomes cannot capture all possible withdrawal experiences. Rat wheel running is not a direct equivalent of human irritability, sleep complaints, appetite changes or distress. Species, dose, route, duration and the inflammatory-pain model restrict translation.
Reduced movement during THC exposure also complicates pain interpretation. A drug may affect movement directly, so a change in running cannot automatically be attributed to pain relief or worsening. The investigators discussed this distinction when comparing activity-based and pain-evoked tests.
The study did not validate a human dependence diagnosis or a blood-concentration threshold. It supports a narrower statement: these particular spontaneous-withdrawal outcomes were not significantly altered after this regimen. It neither guarantees symptom-free cessation in patients nor determines whether a specific person’s symptoms were cannabis-related.
Related analysis: evaluating cannabis tolerance claims.
Primary research
Morgan MM; Hickey CM. 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) (2026). DOI: 10.1002/ejp.70279.
