THC Significantly Reduced Muscle Spasticity in Patients With Neurological Conditions
A double-blind trial found 10 mg of oral THC significantly reduced muscle spasticity in patients with conditions like multiple sclerosis and spinal cord injuries, with the examiner correctly identifying THC trials 78% of the time.
Quick Facts
What This Study Found
Spasticity, the involuntary tightening of muscles, is a common and disabling symptom in conditions like multiple sclerosis, stroke, cerebral palsy, and spinal cord injury. Some patients had reported improvement after smoking cannabis, and animal studies showed THC inhibited certain reflex pathways.
In this double-blind trial, patients received either 10 mg THC, 5 mg THC, or placebo. The blinded examiner correctly identified THC trials in seven of nine cases. At the 10 mg dose, THC significantly reduced spasticity as measured by clinical assessment (P < 0.01). EMG recordings confirmed reduced muscle activity in four patients whose spasticity primarily involved extensor muscles.
In a separate group of eight patients with spasticity from various central nervous system lesions, responses varied. Three of three patients with "tonic spasms" benefited, but patients with cerebellar disease saw no improvement.
Key Numbers
10 mg THC significantly reduced spasticity (P < 0.01). Blinded examiner correctly identified THC in 7 of 9 cases. Three of three patients with tonic spasms benefited. Zero benefit in patients with cerebellar disease.
How They Did This
Double-blind, placebo-controlled trial with oral administration of 5 mg THC, 10 mg THC, or placebo. Muscle tone, reflexes, strength, and EMG were measured before and after dosing. An additional open-label group of eight patients with various CNS conditions was also treated.
Why This Research Matters
This was among the earliest controlled trials demonstrating THC's antispastic effects in humans, providing clinical evidence for what patients had reported anecdotally. The finding that tonic spasms responded well while cerebellar conditions did not suggested THC acts on specific neural pathways rather than producing generalized muscle relaxation.
The Bigger Picture
This early trial helped establish the scientific basis for what eventually became one of cannabis's most recognized medical applications. Decades later, nabiximols (Sativex) was approved in multiple countries specifically for MS-related spasticity, building on evidence that traces back to studies like this one.
What This Study Doesn't Tell Us
Very small sample size. The additional eight patients were treated in an open-label fashion without blinding. The study assessed short-term effects without tracking longer-term outcomes or tolerance development.
Questions This Raises
- ?Why did cerebellar spasticity not respond to THC?
- ?Would sustained dosing maintain the antispastic effect or would tolerance develop?
- ?What is the optimal THC dose for different types of spasticity?
Trust & Context
- Key Stat:
- 10 mg THC significantly reduced spasticity (P < 0.01)
- Evidence Grade:
- A double-blind, placebo-controlled trial with objective measurements including EMG, but with a very small sample size limiting statistical power.
- Study Age:
- Published in 1981. Nabiximols (Sativex) was later developed and approved in many countries for MS spasticity, building on this evidence base.
- Original Title:
- Treatment of human spasticity with delta 9-tetrahydrocannabinol.
- Published In:
- Journal of clinical pharmacology, 21(S1), 413S-416S (1981)
- Authors:
- Petro, D J, Ellenberger, C
- Database ID:
- RTHC-00021
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Did THC help with all types of spasticity?
No. Tonic spasms responded well, but patients with cerebellar disease saw no benefit, suggesting THC acts on specific neural pathways.
What dose was effective?
The 10 mg oral dose produced statistically significant reduction in spasticity. The 5 mg dose was also tested but the abstract focuses on the 10 mg result.
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Cite This Study
https://rethinkthc.com/research/RTHC-00021APA
Petro, D J; Ellenberger, C. (1981). Treatment of human spasticity with delta 9-tetrahydrocannabinol.. Journal of clinical pharmacology, 21(S1), 413S-416S.
MLA
Petro, D J, et al. "Treatment of human spasticity with delta 9-tetrahydrocannabinol.." Journal of clinical pharmacology, 1981.
RethinkTHC
RethinkTHC Research Database. "Treatment of human spasticity with delta 9-tetrahydrocannabi..." RTHC-00021. Retrieved from https://rethinkthc.com/research/petro-1981-treatment-of-human-spasticity
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.