Health effects of marijuana use detailed in large review of recent research
Written by: Alex Lindley
The results of a large review of research on the health effects of cannabis use are in, and the findings were mixed.
The report, from the National Academies of Sciences, Engineering, and Medicine, looked at scientific research on this topic published since 1999. The authors of this report looked at more than 10,000 abstracts and came up with almost 100 “conclusions” on the health effects of marijuana and cannabis products.
“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 Dr. Marie McCormick, chair of the committee behind this new report and a professor at the Harvard T.H. Chan School of Public Health and Harvard Medical School in Boston, in a press release. “This growing acceptance, accessibility, and use of cannabis and its derivatives have raised important public health concerns.”
This report attempted to consider some of those concerns, such as whether marijuana is a “gateway drug” that leads users to other illicit drugs or whether the drug has therapeutic effects for patients with chronic disease.
“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,” Dr. McCormick said. “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.”
The Potential Upsides
In its review, the committee behind this report found evidence that patients with chronic pain who were treated with cannabis or cannabis derivatives called cannabinoids were likely to see decreases in their pain symptoms. These researchers also found that cannabis may help with symptoms of multiple sclerosis and nausea and vomiting related to chemotherapy.
While it’s not exactly an upside, this report did find that, despite what some past research has indicated, there wasn’t much evidence to support the link between smoking marijuana and cancers often linked to tobacco use, such as lung cancer.
The report authors noted a lack of data on cannabis and its effects on immunity, but they did note that limited data suggested cannabis exposure may have anti-inflammatory effects.
Again, not necessarily an upside, but a potential speed bump in assessing marijuana’s negative effects: Despite a common belief that cannabis use has long-term effects on cognitive abilities, this report found limited evidence to support such a link. However, the report authors noted that cognitive abilities were impaired immediately after cannabis use.
The Potential Downsides
Cannabis use was tied to injury in some of the research this report reviewed. For example, using the drug before driving appeared to increase the risk of being involved in a crash.
Also, in states where marijuana use was legal, such as Alaska and Colorado, children faced a raised risk of unintentional cannabis overdose.
Some of the studies this report considered found that smoking marijuana could trigger a heart attack, although the committee behind the report called for more research on the link between cannabis use and diabetes, stroke and heart attack.
Although smoking marijuana didn’t appear to increase the risk for lung cancer, it did appear to increase the risk of other respiratory problems, this report found. Those problems included increased bronchitis episodes and a chronic cough.
Although cannabis use was tied to improved learning and memory abilities in people with schizophrenia and other mental health problems, the report’s findings on cannabis and mental health were largely negative.
“The evidence reviewed by the committee suggests that cannabis use is likely to increase the risk of developing schizophrenia, other psychoses, and social anxiety disorders, and to a lesser extent depression,” according to a press release about the report.
Heavy cannabis use was also tied to more frequent thoughts of suicide. And near-daily users with bipolar disorder were found to have increased symptoms of the mental health disorder.
The more often study participants used marijuana and cannabis products, the more likely they were to develop what the report authors called “problem cannabis use,” this report found. Some evidence also suggested users were more likely to develop abuse problems with other illicit substances.
According to this report, pregnant women may want to avoid smoking marijuana. That’s because smoking the drug during pregnancy was tied to lower birth weights in babies.
The researchers behind this report also looked at barriers to research on the health effects of cannabis. They named as challenges regulatory roadblocks and access to the type of cannabis necessary for research.
The committee called for a network of research funders to support health research on cannabis and cannabis products.
The report provided more detail and additional findings on the health effects of cannabis. It was published in January of 2017.
Funding came from several organizations, including the Centers for Disease Control and Prevention, National Institutes of Health, U.S. Food and Drug Administration, various state agencies and others.