By Pat Anson, Editor

A major new study released today on the health effects of medical marijuana has found “substantial evidence” that cannabis is an effective treatment for chronic pain in adults.

The lengthy study by a committee of the National Academies of Sciences, Engineering, and Medicine looked at over 10,000 scientific reports on marijuana and its active chemical compounds. The committee studied a range of possible impacts marijuana can have on pain, cancer, mental health, injuries and other health conditions.

Marijuana is now the most popular illicit drug in the United States, although it is legal under state law in 28 states and the District of Columbia.

A recent survey found over 22 million Americans have used marijuana in the past month, with nine out of ten users saying their primary use was recreational. Only about 10 percent reported they used cannabis solely for medical purposes. 

“For years the landscape of marijuana use has been rapidly shifting as more and more states are legalizing cannabis for the treatment of medical conditions and recreational use,” said Marie McCormick, the committee chair and a professor of pediatrics at Harvard Medical School.

“This growing acceptance, accessibility, and use of cannabis and its derivatives have raised important public health concerns.  Moreover, the lack of any aggregated knowledge of cannabis-related health effects has led to uncertainty about what, if any, are the harms or benefits from its use.  We conducted an in-depth and broad review of the most recent research to establish firmly what the science says and to highlight areas that still need further examination.”

The committee could find only five good-to-fair quality studies on whether cannabis was an effective treatment for chronic pain.  In all five studies, the cannabis was either smoked or vaporized, and did not include other delivery methods such as food, creams or oils infused with cannabinoids.  

“Thus, while the use of cannabis for the treatment of pain is supported by well-controlled clinical trials... very little is known about the efficacy, dose, routes of administration, or side effects of commonly used and commercially available cannabis products in the United States. Given the ubiquitous availability of cannabis products in much of the nation, more research is needed on the various forms, routes of administration, and combination of cannabinoids,” the committee found.

"It is wonderful to see that what I experience is now being recognized and respected in the medical community," said Ellen Lenox Smith, a PNN columnist who uses marijuana to relieve pain from Ehlers Danlos syndrome.

"I have been allowed nightly rest due to a simple teaspoon of oil at night. Somehow, the next day I rarely need to turn to more, for it continues to calm the body into the next day for me."

Others have also found that cannabis reduces their need for pain relievers. In states where medical marijuana is legal, the committee found growing evidence that users were replacing opioids with cannabis.

“Recent analyses of prescription data from Medicare Part D enrollees in states with medical access to cannabis suggest a significant reduction in the prescription of conventional pain medications,” the committee found. “Combined with the survey data suggesting that pain is one of the primary reasons for the use of medical cannabis, these recent reports suggest that a number of pain patients are replacing the use of opioids with cannabis, despite the fact that cannabis has not been approved by the U.S. Food and Drug Administration (FDA) for chronic pain.”

For adults muscle spasms caused by multiple sclerosis, the committee said there was substantial evidence that short-term use of oral cannabinoids – marijuana-based products that are orally ingested – improved their symptoms.  In adults with chemotherapy-induced nausea and vomiting, there was also conclusive evidence that oral cannabinoids were effective in treating those symptoms.

There was a lack of data on the effects of cannabis on the immune system, and insufficient evidence to support or refute a link between cannabis and adverse effects on the immune status of individuals with HIV.  Limited evidence does suggest that regular exposure to cannabis smoke may have anti-inflammatory effect.

Regarding the link between marijuana and cancer, the committee found evidence that suggests smoking cannabis does not increase the risk for cancers often associated with tobacco use. However, the committee did find that smoking cannabis on a regular basis was associated with more frequent chronic bronchitis, coughing and other respiratory issues.

To download a free copy of the study, click here.