Nearly a quarter of cancer patients reported using cannabis within the past year—and 21 percent did so within the past month—at a cancer center in Washington state, where both medical and recreational marijuana use is legal, according to a recent study report in the journal Cancer.

Survey participants said they used cannabis to relieve cancer symptoms and treatment side effects including pain, nausea and loss of appetite, as well as to improve their mood and help them sleep.

Although legal restrictions have limited formal clinical trials of cannabis for people with cancer and other illnesses, it is now well-established that cannabis has medicinal benefits. As described in a report from the National Academies of Sciences, Engineering, and Medicine released earlier this year, cannabis and isolated chemical components called cannabinoids can reduce chronic pain and help manage chemotherapy-induced nausea. Cannabis use also has some health-related drawbacks, however, including the harmful effects of smoking.

The 2015 National Survey on Drug Use and Health found that 22.2 million Americans—or about 8 percent of people age 12 and older—reported using cannabis within the past month, with about 10 percent saying they do so solely for medical reasons.

Led by California in 1996, nearly half of the states now have medical marijuana laws, with several more legalizing cannabidiol, a cannabis compound that has medicinal effects without the psychoactive properties of tetrahydrocannabinol (THC). Eight states now also allow recreational marijuana use. Washington state legalized medical cannabis in 1998 and marijuana became commercially available for recreational use in 2014.

Steven Pergam, MD, of the Fred Hutchinson Cancer Research Center and colleagues conducted a study of cannabis use among patients at the Seattle Cancer Care Alliance. The Alliance is the outpatient center for a cancer consortium that includes Fred Hutchinson (a National Cancer Institute–designated comprehensive cancer center), the University of Washington and Seattle Children’s Hospital. It serves around 75,000 patients annually from the Northwest and beyond.

Nearly 3,000 eligible adult cancer patients were invited to complete an anonymous 44-question survey about their cannabis use over a six-week period in 2015. Urine samples from a random subset of participants were tested for THC to validate self-reports.

A total of 926 people—around a third of those asked—completed the survey. In this group the median age was 58 and men and women were about equally represented.

Two thirds had various solid tumors (most commonly gastrointestinal, breast, lung and head and necks cancers) while the rest had blood cancers.

Five percent of participants were newly diagnosed with cancer, 66 percent were currently undergoing treatment, 21 percent had finished therapy and 9 percent were not on treatment. Almost all treated patients were using chemotherapy or other medications and 7 percent were receiving radiation therapy. Eighteen percent were undergoing bone marrow transplants, a specialty at Fred Hutchinson.

A majority of respondents (66 percent) said they had used cannabis before, with 24 percent doing so in the past year (defined as “active users”) and 21 percent in the past month. This is more than double the rate for the general population and several times higher than usage rates among older individuals in the age range of typical cancer patients, according to the study authors.

Active users were younger on average, had less education and were less likely to be bone marrow transplant recipients compared with nonusers, but there were no differences according to type of cancer. Age had a strong effect: 40 percent of patients under 30, who made up just 6 percent of all respondents, said they were active cannabis users.

Among the 222 active users, three quarters said they used cannabis at least once weekly and more than half did so daily, including 31 percent who used it more than once a day. Reported frequency of use was consistent with urine test results.

Active users were equally likely to inhale cannabis and consume cannabis-containing edibles (70 percent each), with 40 percent doing both. The most common ways of inhaling were pipes, vaporizers and rolled cigarettes, or joints, while the most common edibles were candy, cannabis butter or oil and homemade baked goods.

Participants said they used cannabis for both physical symptoms and side effects (75 percent) and neuropsychiatric symptoms (63 percent), including the following:

  • Pain
  • Nausea
  • Poor appetite
  • To cope with illness
  • Depression or to improve mood
  • To improve sleep

The researchers noted that although there is scientific evidence for the pain-relieving properties of cannabis, most data come from small studies evaluating chronic neuropathy pain. Evidence supporting cannabis for relieving nausea and improving appetite is mixed, but one survey found that about half of oncologists would recommend it for these symptoms. More research is needed on the benefits of cannabis for managing depression, anxiety and insomnia, they added.

More than a third of study participants said they used cannabis for enjoyment or recreation, but only 7 percent said this was the sole reason. About a quarter said they believed cannabis helped to treat their cancer, and 10 people said they only used it for that reason. Half said cannabis provided a major benefit, while about 40 percent said it offered a moderate benefit.

A quick web search shows that cannabis oil as a cure for cancer is a popular idea. The American Cancer Society offers a brief overview of scientific evidence about cannabis and cancer, noting that although some laboratory and animal studies have shown that cannabinoids may slow the growth of cancer, this has not yet been demonstrated in human clinical trials. Cannabis appears to be safe for cancer patients, but it is risky to use it as a substitute for other types of treatment backed by more research.

Most survey respondents said they had a strong interest in learning about cannabis during cancer treatment. Three quarters said they wanted to get that information from their cancer care team, but less than 15 percent reported receiving such information from a doctor or nurse. Instead, most people got cannabis information from friends and family, other cancer patients, and newspapers, magazines and websites. Of note, more than a third said they hadn’t received any information about cannabis in the context of cancer care.

More than half of respondents said that the fact that cannabis is legal in Washington state increased their likelihood of using it, and this effect was strongest among people who were active marijuana users. Women were more likely than men to say legalization makes them more likely to use it. On the other hand, people who had never used cannabis said legalization did not encourage them to do so.

As a limitation of their study, the researchers noted that only a third of invited participants responded, and people who were using or interested in cannabis may have been more likely to do so. They emphasized that these results may not be representative of cancer patients in states that do not allow legal medical or recreational marijauna use.

“Despite the limited evidence for a medical role for cannabis in oncology, our data suggest that cannabis may be currently used frequently in this setting,” the study authors concluded. “Patients are interested in receiving information about how cannabis might benefit them and prefer that this information come directly from their cancer providers. There is a need for clinical trials evaluating the role of cannabis in symptom management and for the development of formalized education for patients and health care professionals about the risks and benefits of use in this population.”

Click here to read the full Cancer journal article.