Pubdate: Fri, 26 Jun 2015 Source: Arizona Republic (Phoenix, AZ) Copyright: 2015 Associated Press Contact: http://www.azcentral.com/arizonarepublic/opinions/sendaletter.html Website: http://www.azcentral.com/arizonarepublic/ Details: http://www.mapinc.org/media/24 Author: Lindsey Tanner, Associated Press STUDY QUESTIONS IF MARIJUANA EFFECTIVE FOR MANY CONDITIONS CHICAGO (AP) - Medical marijuana hasn't been proved to work for many illnesses that state laws have approved it for, according to the first comprehensive analysis of research on its potential benefits. The strongest evidence is for chronic pain and for muscle stiffness in multiple sclerosis, according to the review, which evaluated 79 studies involving more than 6,000 patients. Evidence was weak for many other conditions, including anxiety, sleep disorders and Tourette's syndrome. The analysis is among several medical marijuana articles published Tuesday in the Journal of the American Medical Association. They include a small study suggesting many brand labels for edible marijuana products list inaccurate amounts of active ingredients. More than half of brands tested had much lower amounts than labeled, meaning users may get no effect. The researchers pooled results from studies that tested marijuana against placebos, usual care or no treatment. That's the most rigorous kind of research but many studies found no conclusive evidence of any benefit. Side effects were common and included dizziness, dry mouth and sleepiness. A less extensive research review in the journal found similar results. It's possible medical marijuana could have widespread benefits, but strong evidence from high-quality studies is lacking, authors of both articles say. "It's not a wonder drug but it certainly has some potential," said Dr. Robert Wolff, a co-author and researcher with Kleijnen Systematic Reviews Ltd., a research company in York, England. Researchers evaluated 47 brands of medical marijuana products, including candy, baked goods and drinks, bought at dispensaries in Los Angeles, San Francisco and Seattle. Independent laboratory testing for THC, marijuana's leading active ingredient, found accurate amounts listed on labels for just 13 of 75 products. Almost 1 in 4 had higher amounts than labeled, which could cause ill effects. Most had lower-than-listed amounts. There were similar findings for another active ingredient. Products were not identified by name. Johns Hopkins University researcher Ryan Vandrey, the lead author, said he was surprised so many labels were inaccurate. The researchers note the results may not be the same in other locations. Twenty-three states and Washington, D.C. have laws permitting medical marijuana use. Approved conditions vary but include Alzheimer's disease, epilepsy, glaucoma, kidney disease, lupus and Parkinson's disease. An editorial in the journal says approval in many states has been based on poor quality studies, patients' testimonials or other nonscientific evidence. The editorial by two Yale University psychiatrists suggests enthusiasm for medical marijuana has outpaced rigorous research and says widespread use should wait for better evidence. Federal and state governments should support and encourage such research, the editorial says. The psychiatrists note repeated recreational marijuana use can be addictive and say questions remain about the long term health effects of medical marijuana use and whether its use is justified in children whose developing brains may be more vulnerable to its effects. - --- MAP posted-by: Jay Bergstrom