Medical cannabis has long been prescribed for treating side effects of chemotherapy, such as nausea, appetite loss, and fatigue. But some news reports take this a step further, claiming that marijuana can actually cure cancer. When determining whether curing cancer with cannabis is a realistic possibility for the majority of cancer patients, we must examine real results from legitimate medical trials to separate fact from fiction.
Can Cannabis Cure Cancer?
Headlines have been touting the use of cannabis to treat cancer. But again, we have to dig a little deeper to get some perspective on what we know, and what we don’t yet know, about the role marijuana products can play in treating cancer.
From the Daily Caller, a headline from 2017 reads, “Weed Is a Cancer Cell Destroyer, Study Finds.” Strong words.
What they’re referring to is a British study that added purified cannabis extracts—not just ordinary weed—to traditional chemotherapy. And it did seem to help kill cancer cells.
But the study was done in a lab, on cancer cells in a dish, not in patients. There’s a big jump between these kinds of pre-clinical studies to actual proof that this will help people.
A somewhat-better, more-accurate headline about the same study from a local TV station read, “Cannabis, Combined with Chemotherapy, Effectively Destroys Cancer Cells.” Still, neither headline and neither story mentioned that the study wasn’t done on actual living people.
Frequently, media stories also tell about individuals who take marijuana and experience amazing results, like this one from The Independent: “Teenager Dying of Cancer Recovers after Mother Gives Him Marijuana.” According to the story, the teen had undergone several rounds of chemo and was not expected to survive.
But he improved markedly after his parents started giving him a cannabis extract they made at home in a pressure cooker, from an online recipe. Stories like this are powerful, and memorable, and you have to cheer this young man’s recovery.
But it’s one story—it’s like flipping a coin, once. We can’t be sure that it was the cannabis that made the difference.
This is a transcript from the video series The Skeptic’s Guide to Health, Medicine, and the Media. Watch it now, on The Great Courses Plus.
Most important, we don’t know how many other families in the UK tried cannabis as treatment for loved ones with cancer, and how many of them didn’t do well.
Newspapers don’t report the sad news—that’s all too commonplace—that teens and adults die of cancer, every day. In a research study, we can know how many people tried cannabis, and their outcomes, because we track a group of people.
Personal stories in newspapers are not scientific studies. There’s a big difference between anecdotes and systematically collected data.
Nonetheless, there does seem to be genuine evidence that chemicals in the marijuana plant may have cancer-fighting properties. Better research is needed to understand which compounds are effective and how to use them to fight which kinds of cancer. There’s promise there, but still a lot of work to be done.
Learn more about medical marijuana’s safety and usefulness
Treating Chemo Side Effects with Cannabis
There’s another way that cannabis might help cancer patients—cannabis used not just to treat cancer itself, but perhaps to treat the side effects of traditional cancer treatments, like chemotherapy. Side effects like nausea and vomiting, appetite loss and fatigue, can be huge problems.
But is cannabis the answer? Newsweek seems to think it is. In 2015, the magazine’s headline proclaimed “Marijuana Is a Wonder Drug When It Comes to the Horrors of Chemo.”
The story is another good example of the kind of reporting that we’re seen before: headlines that grab you, but stories that lack solid details. Newsweek’s story starts with anecdotes—positive experiences from cancer patients and oncologists who’ve been helped by cannabis.
But then, further down in the same article, the best evidence we have for the use of medical cannabis is finally mentioned, in this case quoting a 2015 systematic review of the literature. The article included 79 solid studies of the use of cannabinoids for several medical conditions, including the side effects of chemo.
The studies, combined, accounted for over 6,000 studied patients. That’s an admirably large number.
Newsweek states that based on that review of the medical literature, “Most who used cannabinoids reported improvements to symptoms compared with patients in placebo groups.” That sounds convincing.
But the very next sentence in the Newsweek article contradicts that claim: “These improvements were not statistically significant.”
These contradictory statements means that the difference between the two measurements was very unlikely to have occurred by chance alone. Cannabis was only as effective as a placebo in these studies, which means, as far as we can measure, that it did not work to ameliorate most of the symptoms associated with chemotherapy.
Here’s the bottom line: Don’t believe a result to be true unless it is statistically true. No statistical difference means, simply, no difference.
Key Points for Evaluating Medical Journalism
- Headlines: Headlines can be deceiving. You need to read beyond the headlines. Be especially wary of words like “miracle” or “wonder drug”—those pretty much guarantee an exaggerated, unbalanced article.
- Source: When you look at reports of studies, consider the publisher and the source of the study. Is it a professional news site or a blog, and has the study been published in an established, peer-reviewed journal?
- Numbers: Think about how many subjects were involved, and make sure the conclusions were statistically significant.
- Evidence: Always be wary of anecdotes. They make good story leads, but they’re not data. Data includes concepts like the number of subjects and whether the results reached statistical significance. A strong story has solid medical evidence behind it.
Learn more about how to ask the questions that take you past the headlines
Medical Cannabis: A Word of Caution
We’ve seen that for many indications, there isn’t great evidence that medical cannabis works—some tantalizing clues, some pre-clinical evidence, many anecdotes, but precious little hard, rigorous data.
In 2017, the National Academies of Science reviewed over 10,000 studies on cannabis products to treat medical conditions. This endeavor was a very rigorous review, and all 487 pages of the hefty report are available for as a free download.
The National Academies of Science concluded that there was good evidence to support the use of cannabis as medicine for three conditions: to relieve chronic pain in adults, to lessen chemotherapy-induced nausea and vomiting, and to relieve some symptoms of multiple sclerosis.
They also felt that there was “moderate” evidence for relieving some sleep problems associated with certain medical conditions. That’s it. Even then, we have zero evidence for exactly what kinds of cannabis compounds to use in what dose to treat these conditions.
But, so what? What’s the harm in having people just try it, to see if it helps?
The biggest drawback is the potential side effects. In a 2017 article in the Observer, “Medical Marijuana Isn’t a Miracle Drug,” the author points out that, “For some, cannabis can cause the very symptoms it’s trying to prevent.”
Cannabis compounds can contribute to anxiety and paranoia and have been linked to schizophrenia. In some people, it increases the risk of seizures and can cause nausea and loss of appetite.
Some of the trials using cannabis for pain featured a high drop-out rate. Many of the patients couldn’t tolerate the side effects of the cannabis and dropped out of the study.
Cannabis compounds, and not just THC, affect cognition and memory, and may have especially worrisome long-term effects when used by children and teens whose brains are still developing.
Smoking marijuana—not just ingesting the medical compounds or extracts, but smoking the plant—can have even more deleterious effects.
None of this should disqualify cannabis as a potential medicine. After all, all real medicines have potential side effects, many of which are even more serious or more common than those seen with cannabis.
What it does mean, though, is that cannabis is really just like any other drug. It may have some uses, and some important benefits for some people, but those have to be weighed against potential side effects, as we’d do with any other drug.
Marijuana, as well as any other “natural remedies,” should be held to the same standards as medicines. But cannabis hasn’t been treated in the media or in public perception as just another medication.
Medical marijuana use has not been driven by the medical community or pharmaceutical industry. And, generally, it has not been the product of rigorous, well-designed studies.
Communities that have approved medical marijuana use are doing this through a legislative process driven by activists, patients, and ballot initiatives. That’s not a bad thing if it results in better treatments that help people.
However, we still have to ask the tough questions to know if what we’re doing is the right thing.