Excerpt from About.com: (click for entire article)
I'll admit, I found it a little weird to see this all over the news of the multiple sclerosis world. I kind of thought we already pretty much knew that marijuana helped with certain MS symptoms.
I guess the big news here is that this was a well-run, rigorous (albeit small) study. In this study, published in the Canadian Medical Association Journal, researchers used a crossover design - 30 people smoked either a marijuana cigarette (joint) or a placebo (that looked, tasted and smelled just like the real deal, but lacked active ingredients) once a day for 3 days in a row. Then they switched to the other (marijuana or placebo) for 3 days. It should be noted that these 30 participants were people who had MS-related spasticity and had failed to respond to other treatments.
Here is what researchers found:
Participants saw a 30 percent improvement in measures of spasticity after smoking the marijuana, but not after the placebo.
Smoking marijuana significantly reduced pain scores (by 5.28 points on a visual analog scale) over placebo.
Smoking the marijuana caused fatigue and dizziness and slowed down cognitive function soon after smoking.