Smoking marijuana has been shown to relieve muscle tightness, called spasticity, and painful symptoms in patients with multiple sclerosis, who have been resistant to conventional MS therapies, according to a new study.

"We found that smoked cannabis was superior to placebo in reducing symptoms and pain in patients with treatment-resistant spasticity, or excessive muscle contractions," Researcher Dr. Jody Corey-Bloom, director of the University of California, San Diego Multiple Sclerosis Center said in a journal news release.

However, the latest findings from the small study, showed that the benefits of cannabis is paired with some cognitive effects, researchers warned.

Individuals with multiple sclerosis often suffer from spasticity, an painful and often disabling condition in which the muscles tighten and become difficult to control, and while there are some drugs that relieve spasticity, these traditional treatments often fail to work and come with many side effects.

Corey-Bloom and her colleagues studied 30 multiple sclerosis patients with who suffer from spasticity and did not respond will to conventional drugs.

The average age of all the patients in the study was 50, and half of the participants need walking aids and a fifth used wheelchairs.

Participants were randomly assigned either into the intervention, where patients would smoke cannabis once a day for three days or control group, where patients would smoke identical placebo cigarettes for the same amount of time.

Corey-Bloom found that while all participants weren’t helped by available treatments, patients who smoked marijuana experienced a nearly one-third decrease on the Ashworth scale at 2.74 points from the baseline score of 9.3, which meant spasticity had significantly improved, compared to the placebo group.  

Researchers explained that a difference of two or more points has clinical significance of the 30-point Ashworth scale summing mobility of elbows, hips, and knees.

Pain scores which started at an average of 12 or 13 on the 100-point Visual Analogue Scale, dropped by 5.28 points, or an additional 50 percent in the marijuana group compared to the placebo group, according to researchers.

"We saw a beneficial effect of smoked cannabis on treatment-resistant spasticity and pain associated with multiple sclerosis among our participants," researchers wrote in the study published online in the Canadian Medical Association Journal.

Researchers said while there were benefits to smoking marijuana, there was also reduced cognitive function in the marijuana group compared to the placebo group. 

Participants in the marijuana group scored 8.67 points lower in the Paced Auditory Serial Addition Test, which was administered 45 minutes after smoking, compared to the control group.

"Although generally well-tolerated by our participants, smoking cannabis was accompanied by acute cognitive effects."

However researcher noted that "the clinical significance of this result is uncertain; despite the transient decrease in scores, patients were still within normal ranges for their ages and levels of education," the investigators pointed out in the paper.

"It is worth noting that conventional treatments, such as baclofen and tizanidine hydrochloride, may also affect cognition, although published data are scarce," they added.

Researchers said findings that illustrate the benefits of cannabis have generally been anecdotal evidence from many patients with multiple sclerosis who say that smoking marijuana relieved spasticity, and other clinical trials, which have mainly focused on orally administering cannabinoids, had produced mixed results.

"Any reductions in spasticity have generally only been seen on subjective ratings," researchers noted.

"Using an objective measure, we saw a beneficial effect of inhaled cannabis on spasticity among patients receiving insufficient relief from traditional treatments," the authors concluded. "Although generally well-tolerated, smoking cannabis had acute cognitive effects. Larger, long-term studies are needed to confirm our findings and determine whether lower doses can result in beneficial effects with less cognitive impact."