En español | Evaluating medical marijuana research disease by disease is not easy, hampered as it is by the federal government’s ban on government-supported data collection. Observational studies — in which users simply report their experiences — may look rosy. Animal and test-tube studies also can sound promising. But plenty of stuff that helps mice or a clump of cells in a petri dish may not help us humans. Despite these obstacles, there are some conditions and diseases for which cannabis is clearly a useful treatment. Others, not so much.
Nearly 1 million Americans, including many 45 and older, live with the debilitating muscle spasms and pain of multiple sclerosis. Up to 66 percent of them may be using medical marijuana, a 2017 survey found. It’s likely they’ve cut back on MS medications, too. In fact, people with MS are the second-largest group of medical marijuana users in the U.S., behind chronic pain sufferers. There’s substantial science for cannabis’ ability to reduce MS muscle spasms. Meanwhile, others are looking at a potential cannabis-based drug for MS. The cannabis research and development company MMJ International Holdings Corp. hopes to test an experimental medication — a highly purified, liquid plant extract with THC and CBD in a gelatin capsule — for MS in the U.S. soon.
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Cannabis is highly effective for cancer pain and the side effects of cancer treatment — nausea, vomiting, loss of appetite and weight loss, says Donald Abrams, an oncologist and professor of medicine at the University of California San Francisco and a longtime advocate of medical marijuana. “There’s no question in my mind, it works,” Abrams says. “I was on the NASEM committee that reviewed the evidence.”
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In addition, several other marijuana-based medications have been approved or are undergoing clinical trials. Nabiximols (Sativex ® ), a mouth spray that is currently available in the United Kingdom, Canada, and several European countries for treating the spasticity and neuropathic pain that may accompany multiple sclerosis, combines THC with another chemical found in marijuana called cannabidiol (CBD).
A new study underscores the need for additional research on the effect of medical marijuana laws on opioid overdose deaths and cautions against drawing a causal connection between the two. Early research suggested that there may be a relationship between the availability of medical marijuana and opioid analgesic overdose mortality. In particular, a NIDA-funded study published in 2014 found that from 1999 to 2010, states with medical cannabis laws experienced slower rates of increase in opioid analgesic overdose death rates compared to states without such laws. 78
Medical Marijuana Laws and Prescription Opioid Use Outcomes
The potential medicinal properties of marijuana and its components have been the subject of research and heated debate for decades. THC itself has proven medical benefits in particular formulations. The U.S. Food and Drug Administration (FDA) has approved THC-based medications, dronabinol (Marinol ® ) and nabilone (Cesamet ® ), prescribed in pill form for the treatment of nausea in patients undergoing cancer chemotherapy and to stimulate appetite in patients with wasting syndrome due to AIDS.
A 2019 analysis, also funded by NIDA, re-examined this relationship using data through 2017. Similar to the findings reported previously, this research team found that opioid overdose mortality rates between 1999-2010 in states allowing medical marijuana use were 21% lower than expected. When the analysis was extended through 2017, however, they found that the trend reversed, such that states with medical cannabis laws experienced an overdose death rate 22.7% higher than expected. 79 The investigators uncovered no evidence that either broader cannabis laws (those allowing recreational use) or more restrictive laws (those only permitting the use of marijuana with low tetrahydrocannabinol concentrations) were associated with changes in opioid overdose mortality rates.
An additional concern with “medical marijuana” is that little is known about the long-term impact of its use by people with health- and/or age-related vulnerabilities—such as older adults or people with cancer, AIDS, cardiovascular disease, multiple sclerosis, or other neurodegenerative diseases. Further research will be needed to determine whether people whose health has been compromised by disease or its treatment (e.g., chemotherapy) are at greater risk for adverse health outcomes from marijuana use.