A report from the National Academies of Sciences, Engineering, and Medicine – published on 12th January, 2017 – consolidated all evidence published since 1999 regarding the health impacts associated with cannabis and cannabis-derived products, such as marijuana.
In excess of 10,000 scientific abstracts were considered by the committee that carried out the study and wrote the report in order to reach its nearly 100 conclusions.
The growing accessibility of cannabis and acceptance of its use for recreational purposes have raised important public health concerns. Neither the level of therapeutic benefit offered by the drug nor the risks it carries for causing adverse health effects have been rigorously assessed.
“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, chair of the committee; the Sumner and Esther Feldberg Professor of Maternal and Child Health, department of social and behavioral sciences, Harvard T.H. Chan School of Public Health; and professor of pediatrics, Harvard Medical School, Cambridge, Mass.
“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. As laws and policies continue to change, research must also.”
A scientific research committee has reviewed all evidence relating to the health impacts of taking cannabis and other related cannabinoids, such as marijuana, published since 1999.
The committee concluded that the evidence supports therapeutic use of cannabis and cannabinoids for treating chronic pain in adults, muscle spasms in adults with multiple sclerosis, and chemotherapy-induced nausea and vomiting in adults.
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 – such as lung and head and neck cancers. The committee also found limited evidence that cannabis use is associated with one sub-type of testicular cancer.
There is a lack of data on the effects of cannabis or cannabinoid-based therapeutics on the human immune system, as well as insufficient data to draw overarching conclusions concerning the effects of cannabis smoke or cannabinoids on immune competence, the committee stated. There is also insufficient evidence to support or refute a statistical association between cannabis or cannabinoid use and adverse effects on immune status in individuals with HIV. Nevertheless, limited evidence suggests that regular exposure to cannabis smoke may have anti-inflammatory activity.
Although the committee highlighted the need for further research into the association between cannabis use and death or occupational injury, current evidence indicates that the risk of being involved in a motor vehicle accident is increased when driving after taking cannabis.
There was no evidence indicating that smoking cannabis carries the same increased risk for cancer as smoking tobacco. However, it does appear that smoking cannabis is associated with chronic bronchitis and other respiratory symptoms.
The committee concluded that cannabis use typically has negative effects on mental health, increasing the risk of developing schizophrenia and social anxiety disorders and worsening symptoms in people with bipolar disorder. Interestingly, although learning, memory, and attention are impaired immediately after cannabis use, a history of cannabis use may improve performance on learning and memory tasks.
More research is needed to determine the effects of cannabis use on the risk of developing cardiovascular or respiratory diseases, and on the human immune system.
The committee also proposed ways to advance understanding of the effects of cannabis use as regulatory and access barriers currently make it difficult to conduct the necessary research. They concluded that a diverse network of funders is needed to support cannabis and cannabinoid research.
- National Academies of Sciences, Engineering, and Medicine Press Release. 12 January 2017. Available at https://www.eurekalert.org/pub_releases/2017-01/naos-heo011217.php