THC Significantly Reduced Muscle Spasticity in Patients With Neurological Conditions | Research

The takeaway

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.

Read this if you have a condition involving muscle spasticity and want to know what early clinical research found about THC.

10 mg THC significantly reduced spasticity (P < 0.01)

What the researchers 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.

Why it 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 numbers in context

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 the study worked

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.

What this study cannot 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.

How to read the evidence

A double-blind, placebo-controlled trial with objective measurements including EMG, but with a very small sample size limiting statistical power.

When this study was published

Published in 1981. Nabiximols (Sativex) was later developed and approved in many countries for MS spasticity, building on this evidence base.

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.

Questions still open

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?

Common 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.

Read the original research

Treatment of human spasticity with delta 9-tetrahydrocannabinol.

Journal of clinical pharmacology, 21(S1), 413S-416S

View on PubMed ↗

Citation

Petro, D J; Ellenberger, C. (1981). Treatment of human spasticity with delta 9-tetrahydrocannabinol.. Journal of clinical pharmacology, 21(S1), 413S-416S.