The researchers conclude that cannabis could be beneficial for chronic pain, but it may increase the risk of mental health problems.
Cannabis is a drug derived from the plant Cannabis sativa. It is most commonly used in the form of marijuana, which is produced from the dried leaves of the cannabis plant.
According to the National Institute on Drug Abuse, marijuana is the most commonly used illicit drug in the U.S. In 2014, approximately 22.2 million people in the country reported using marijuana over the course of a month.
However, to date, 28 states and the District of Columbia have legalized marijuana for medicinal purposes, with recreational use permitted in some of these states.
Marie McCormick, chair of the National Academies of Sciences, Engineering, and Medicine committee, says that the increased legalization of cannabis and its derivatives is making the drug more accepted and accessible. This has led to increased use, which has "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," adds McCormick, who is also the Sumner and Esther Feldberg Professor of Maternal and Child Health at the Department of Social and Behavioral Sciences at Harvard T.H. Chan School of Public Health in Boston, MA, and a professor of pediatrics at Harvard Medical School in Cambridge, MA.
Cannabis: How does it impact health?
With this in mind, McCormick and colleagues from the National Academies of Sciences, Engineering, and Medicine committee analyzed the data of more than 10,000 scientific studies on the health effects of cannabis and cannabis-derived products - including marijuana and cannabinoids, the active components of cannabis - that had been published since 1999.
Specifically, the researchers looked at the therapeutic potential of cannabis and its derivatives, as well as the health risks associated with its use. Medical News Today take a look at some of the key findings.
The researchers recently published their results in a report titled "The health effects of cannabis and cannabinoids: The current state of evidence and recommendations for research (2017)."
'Substantial evidence' that cannabis treats chronic pain
Chronic pain is estimated to affect more than 25 million U.S. adults, and it is a leading cause of disability.
When it comes to medicinal cannabis, one of its key uses is for the treatment of chronic pain. In the new report, researchers found that patients with chronic pain who were treated with cannabis or products containing cannabinoids were more likely to report significant pain relief than untreated patients.
Based on their analysis, the National Academies of Sciences, Engineering, and Medicine conclude:
"There is substantial evidence that cannabis is an effective treatment for chronic pain in adults."
Cannabis use may harm mental health
A number of studies have suggested that cannabis use can have negative implications for mental health, and from their scientific review, the National Academies of Sciences, Engineering, and Medicine conclude that this is the case.
The researchers uncovered "substantial evidence" that cannabis use is "likely to increase the risk of schizophrenia and other psychoses," and the more the drug is used, the higher the risk.
The team also found evidence that daily cannabis use may exacerbate symptoms of bipolar disorder for patients with the condition.
Additionally, "moderate evidence" suggests that frequent users of cannabis may be more likely to report suicidal thoughts and that regular use of the drug could increase the risk of social anxiety disorder. Cannabis use may also pose a "small increased risk" for the development of depressive disorders.
However, the researchers conclude that there is "limited evidence" of a statistical link between cannabis use and the development of bipolar disorder, and there is "no evidence" to either support or refute a statistical link between cannabis use and the development of post-traumatic stress disorder.
Cannabis and cancer risk
It is well established that smoking tobacco can increase the risk of lung, head, and neck cancers, and some studies have suggested that smoking cannabis can do the same.
The new report, however, concludes that there is no evidence of a statistical link between cannabis use and the risk of lung cancer and head and neck cancers.
The researchers uncovered "moderate evidence" of a link between cannabis use and one subtype of testicular cancer - seminoma testicular cancer, a slow-growing form of the disease.
Furthermore, the team found no evidence of a link between marijuana use in pregnancy and cancer risk in offspring.
In relation to nausea and vomiting caused by chemotherapy, the researchers found that the use of cannabinoids may help to treat or prevent these symptoms.
Recommendations for future cannabis research
While the new report helps to clarify some of the benefits and risks of using cannabis and its derivatives, the National Academies of Sciences, Engineering, and Medicine say that further research is warranted.
The organization makes a number of recommendations for future studies into the health effects of cannabis use. These include:
- Researchers should assess the health effects of cannabis use in children and adolescents, as this population is understudied
- Well-controlled studies that investigate the possible benefits and harms of different forms of cannabis, such as oral cannabis and inhaled whole cannabis, should be conducted
- Studies should assess the potential benefits and risks of currently understudied cannabis products, such as edible and topical cannabis.
Additionally, the authors of the report say that efforts should be made to break down the barriers currently preventing more advanced research into the health effects of cannabis use, such as cannabis being classified as a Schedule I substance. This classification states that the drug has a high potential for abuse and has no accepted medical use.
"To ensure that policymakers are better informed to make decisions on cannabis research and policy, and to explore and characterize the full scope of political and non-political strategies for resolving regulatory barriers to cannabis research, an objective and evidence-based analysis of cannabis policy is necessary," say the report authors.