Smoking marijuana to relieve the symptoms of multiple sclerosis is a practice with a fair number of adherents, though it has not been subject to rigorous testing. A new study finds that puffing weed does have a rapid and measurable effect on MS patients’ muscle spasticity and on their perception of pain. But subjects who smoked pot were not able to walk any faster and -- surprise! -- they felt higher than members of the control group who smoked marijuana stripped of THC.

The study, published Monday in the Canadian Medical Association Journal, recruited 30 MS patients who suffered from spasticity -- stiffness and involuntary muscle spasms that are a common symptom of MS -- as well as from pain, usually in the back. Divided into two groups, each group got marijuana and placebo marijuana, with a “wash-out” period of eleven days, during which neither was taken. Forty-five minutes after smoking placebo or cannibis cigarettes -- provided by the National Institute on Drug Abuse-- subjects were administered a test of muscle tone in the elbows, hips and knees, a walking-speed test, a pain inventory and a test gauging cognitive symptoms.

Past tests have found that orally administered cannabinoids elicit subjective improvements in spasticity among those with MS, but no evidence of actual change. And anti-spasmodic medications, including baclofen and tizanidine, reduce spasticity in many patients. But while those appear to have some ill-defined cognitive side effects, there was no ambiguity in smoked marijuana’s effect: “Though generally well-tolerated by our participants, smoking cannibus was accompanied by acute cognitive effects,” the authors wrote. Future studies, they said, should focus on whether less than a full cigarette’s worth of cannibis could have the same benefits with a less intense high.