Marijuana has proved to be a powerful aid in easing chronic pain and helping battle nausea, but results are mixed or largely inconclusive on other health benefits, as well as detriments, according to a massive new scientific review of cannabis studies.
The report, released Thursday by the National Academies of Science, Engineering, and Medicine, analyzes an astounding 10,000 scientific studies on the drug. “The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research” concludes that marijuana definitely provides some health benefits, though other claims about the drug are far less clear. The scientists note that much information could be determined if researchers didn’t have to battle restrictions caused by federal classification of cannabis as a Schedule 1 drug, meaning it “currently” has “no accepted medical use and a high potential for abuse.”
“It is often difficult for researchers to gain access to the quantity, quality, and type of cannabis product necessary to address specific research questions on the health effects of cannabis use,” conclude the authors, a panel of experts led by Harvard public health researcher Marie McCormack.
Federal attitude aside, more than half of all U.S. states have legalized marijuana for medical use, and eight (plus the District of Columbia) have legalized the drug for recreational use.
The major conclusions in the study are that cannabis and cannabinoids are effective at “significantly reducing” chronic pain, particularly linked to muscle spasms caused by multiple sclerosis. There’s also “conclusive evidence” that cannabis is effective at preventing and treating nausea related to chemotherapy.
There is “moderate evidence” that cannabis and cannabinoids are effective for improving “short-term sleep outcomes” for people suffering sleep disturbances linked to sleep apnea, fibromyalgia and chronic pain. The study also finds “limited evidence” that cannabis and cannabinoids are effective in increasing appetite and improving anxiety and post-traumatic stress symptoms.
“It is often difficult for researchers to gain access to the quantity, quality, and type of cannabis product necessary to address specific research questions on the health effects of cannabis use.”
- study authors
There is insufficient or no evidence, however, to support — or refute — use of the drug for several other ailments and problems including cancer, epilepsy, addiction, schizophrenia and Parkinson’s disease, the report concludes.
On the negative side, the review finds that use of marijuana may increase the risk of developing mental health issues, such as schizophrenia, anxiety and, to a lesser extent, depression — though it’s also possible that people with these problems turn to marijuana for help and skew the results, the report notes.
It isn’t linked to lung and neck cancers associated with smoking tobacco, but frequent use can cause or exacerbate respiratory problems, the study concludes. Smoking marijuana while pregnant may be linked to lower birth weights, but it’s not clear if there are any long-term effects to children born to moms who smoked pot while pregnant. “Some evidence suggests smoking marijuana may trigger a heart attack among individuals with diagnosed heart disease,” according to the study review.
There’s substantial evidence that driving under the influence causes an “increased risk of motor vehicle crashes,” the report concludes. It also warns that increasing numbers of children may be accidentally ingesting marijuana now that it’s more widely available.
The evidence that marijuana is a gateway drug to trying other drugs “is limited,” the study says. But researchers also found “moderate evidence” of a link between cannabis use and the development of substance dependence or abuse problems with alcohol, tobacco and illegal drugs.
The review of studies was an attempt to pinpoint the gaps in knowledge about marijuana use and call for rigorous research into the drug as it becomes more easily available. “This is a pivotal time in cannabis research,” the report notes.
President-elect Donald Trump’s nominee for U.S. attorney general, Sen. Jeff Sessions (R-Ala.), could keep the nation in marijuana suspense. He is known as a steadfast opponent of legalizing marijuana but had only vague answers at his confirmation hearing Thursday about what he’d do about pot if he is confirmed.