Medical marijuana is a controversial topic, but a new study offers support for its use in one serious condition. People with multiple sclerosis have long claimed that marijuana can relieve or prevent painful muscle spasms. Doctors have classified these testimonials as questionable anecdotes. A study at the University of California, San Diego enrolled 30 MS patients who had not responded well to conventional medicine. They were given marijuana or placebo joints in this double-blind crossover study. Muscle spasticity decreased by about 30 percent on the days that the volunteers smoked marijuana. Some people felt tired, dizzy or spacy on those days. The investigators admit that the blinding was imperfect. Although the placebo joint looked, smelled and tasted like marijuana, it did not produce a marijuana high.