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The role of legalized marijuana in society and evidence-based medicine was examined at the ACR/ARHP Annual Meeting.
As local governments move toward legalization of marijuana, many patients who have rheumatic diseases are curious about how cannabinoids might contribute to treatment of their condition.
The role of legalized marijuana in society, as well as in the practice of evidence-based medicine, was examined in a November 6 presentation at the ACR/ARHP Annual Meeting in San Diego.
In the United States, marijuana remains a Schedule I controlled substance under federal law. However, 23 states and the District of Colombia have passed local laws that allow for the medical use of cannabis and 7 states and the District of Colombia have legalized marijuana for recreational use.
Implications for society
Rosalie Pacula, PhD, a senior economist at the RAND Corporation, led the presentation by explaining that the scientific community took decades to learn all that it currently knows about the health effects of tobacco and alcohol but most research on the effects of cannabis is stymied by federal restrictions that block researchers’ access, slowing the research process and making a lot of the available data less reliable.
The United States faces a patchwork of state laws that cover the sale, possession, and prescription of cannabis. Many of the laws legalizing the use of cannabis have been passed faster than the scientific community can collect the data necessary to help weigh the health, safety, and ethical ramifications.
“Policy doesn’t wait for scientific research,” Dr Pacula said, and given the sizable tax revenue currently being made from cannabis sales, this is unlikely to change in the future. In 2016, for example, Colorado reported $193.6 million in cannabis tax revenue and Washington reported $189.2 million.
Studies consistently suggest an increase in adult marijuana use since legalization, but Dr Pacula said it is still too early to determine whether this is a good or bad thing. Part of the difficulty in interpreting data comes from heterogenicity between jurisdictions where use is legalized, because laws vary considerably between states. Sometimes there is a time lag between policy passage and full policy implementation, and many state policies continue to evolve over time.
Many more questions about marijuana use need to be answered before the implications for society can be fully understood.
For example, how is marijuana most frequently consumed and with what other substances? How does the market influence product potency, offering, and safety? How can the dose-response relationships be better measured?
Dr Pacula concluded that drawing strong conclusions from the policy evaluations conducted thus far would be dangerous.
Potential of cannabinoids as therapeutic agents
From the evidence-based medicine perspective, Dr Daniele Piomelli, director of the Institute for the Study of Cannabis at the University of California Irvine, discussed the effects of cannabinoids on CNS and peripheral nervous system function as well as the diseases in which cannabinoids have been tested formally.
Dr Piomelli cautioned that information coming from the cannabis industry is not always based on data, citing a study that found 90% of marijuana dispensary staff admitted to dispensing advice even though only 10% had relevant education to do so.
Although the list of potential therapeutic indications for cannabis is long, only a few are actually supported by data. Dr Piomelli was a member of a National Academy of Sciences committee that released a report on this topic in January 2017, based on a review of 10,000 published studies. The report concluded that there was substantial evidence of the effectiveness of cannabis for chronic pain, nausea and vomiting, and multiple sclerosis.
However, contradicting many widely held assumptions about the myriad benefits of cannabis, the committee found insufficient evidence of effectiveness for amyotrophic lateral sclerosis, epilepsy, Huntington disease, irritable bowel syndrome, and Parkinson disease and limited evidence of ineffectiveness for dementia, depression, and glaucoma. For cancer, there was insufficient evidence to support or refute the effectiveness of cannabis.
The NAS report and Dr Piomelli recommend expansion of cannabis research and enhanced data collection, which would require the federal government to change the scheduling of marijuana so that scientists could access it for study.
Additional research might help scientists determine whether cannabis is appropriate for treating pain associated with rheumatic diseases, whether increased cannabis use might affect the opioid crisis, and perhaps whether endocannabinoid signals might be used for therapy.
4M122ARHP: Cannabis in Society and Medical Practice. Presented at: 2017 ACR/ARHP Annual Meeting; November 3-8, 2017; San Diego, California.