CHICAGO (AP) — Medical
marijuana has not been proven 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 and the authors
recommend more research.
The analysis is among several medical
marijuana articles published Tuesday in the Journal of the American
Medical Association. They include a small study suggesting that 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 might get no effect.
Highlights from the journal:
THE ANALYSIS
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.
EDIBLE PRODUCTS
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, however, that the results may not be
the same in other locations.
MARIJUANA LAWS
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.
Marijuana is illegal under federal law and some
scientists say research has been stymied by government hurdles including
a declaration that marijuana is a controlled substance with no accepted medical use.
But in a notice published Tuesday in the Federal Register,
the Department of Health and Human Services made it a little easier for
privately funded medical marijuana research to get approved. The
department said that a federal Public Health Service review of research
proposals is no longer necessary because it duplicates a required review
by the Food and Drug Administration.
THE FUTURE
Colorado,
one of a few states where recreational marijuana use is legal, has
pledged more than $8 million in state funds for several studies on the
drug's potential medical benefits, including whether it can reduce
veterans' symptoms of post-traumatic stress disorder. That study may
begin recruiting participants later this year, said Vandrey, one of that
study's leaders.
Vandrey said there's a feeling of optimism in
the research community that "we'll start to get a good science base" for
the potential medical uses of marijuana.
THE RECOMMENDATIONS
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.
"Perhaps
it is time to place the horse back in front of the cart," Drs. Deepak
Cyril D'Souza and Mohini Ranganathan wrote in the editorial.
They
note that repeated recreational marijuana use can be addictive and say
unanswered questions include what are 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.
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