Principal investigator Dr. Jody Corey-Bloom, professor of neurosciences and director of the Multiple Sclerosis Center at the University of California, San Diego, and colleagues randomly assigned 30 study participants to either the intervention group -- which smoked marijuana once daily for three days -- or the control group. After an 11-day interval, the participants crossed over to the other group.
"We found that smoked cannabis was superior to placebo in reducing symptoms and pain in patients with treatment-resistant spasticity, or excessive muscle contractions," Corey-Bloom said in a statement.
The researchers used a modified Ashford scale to grade the intensity of muscle tone by measuring such things as resistance in range of motion and rigidity. The researchers also looked at physical performance -- using a timed walk -- and cognitive function. Patients were also asked assess their feeling of "highness."
The study published in the Canadian Medical Association Journal found the marijuana was generally well tolerated, but it has mild effects on attention and concentration.
The researchers noted that larger, long-term studies were needed to confirm their findings.