Cannabis and Cannabinoids (PDQ®): Integrative, alternative, and complementary therapies – Patient Information [NCI]
Questions and Answers About Cannabis
Cannabis, also known as marijuana, is a plant first grown in Central Asia that is now grown in many parts of the world. The Cannabis plant makes a resin (thick substance) that contains compounds called cannabinoids. Some cannabinoids are psychoactive (affecting your mind or mood). In the United States, Cannabis is a controlled substance and has been classified as a Schedule I agent (a drug with a high potential for abuse and no accepted medical use).
Clinical trials that study Cannabis for cancer treatment are limited.
By federal law, possessing Cannabis (marijuana) is illegal in the United States unless it is used in approved research settings. However, a growing number of states, territories, and the District of Columbia have passed laws to legalize medical marijuana. (See Question 3).
What are cannabinoids?
Cannabinoids, also known as phytocannabinoids, are chemicals in Cannabis that cause drug-like effects in the body, including the central nervous system and the immune system. The main psychoactive cannabinoid in Cannabis is delta-9-THC. Another active cannabinoid is cannabidiol (CBD), which may relieve pain and lower inflammation without causing the high of delta-9-THC.
Cannabinoids may help treat the side effects of cancer and cancer treatment.
If Cannabis is illegal, how do some cancer patients in the United States use it?
Although federal law prohibits the use of Cannabis, the map below shows the states and territories that have legalized Cannabis for medical purposes. Some other states have legalized only one ingredient in Cannabis, such as cannabidiol (CBD), and these states are not included in the map. Medical marijuana laws vary from state to state.
A map showing the U.S. states and territories that have approved the medical use of Cannabis.
How is Cannabis given or taken?
Cannabis may be taken by mouth (in baked products or as an herbal tea) or may be inhaled. When taken by mouth, the main psychoactive ingredient in Cannabis (delta-9-THC) is processed by the liver and changed into a different psychoactive chemical (11-OH-THC).
When Cannabis is smoked and inhaled, cannabinoids quickly enter the bloodstream. The psychoactive chemical (11-OH-THC) is made in smaller amounts than when taken by mouth.
A growing number of clinical trials are studying a medicine made from an extract of Cannabis that contains specific amounts of cannabinoids. This medicine is sprayed under the tongue.
Have any laboratory or animal studies been done using Cannabis or cannabinoids?
In laboratory studies, tumor cells are used to test a substance to find out if it is likely to have any anticancer effects. In animal studies, tests are done to see if a drug, procedure, or treatment is safe and effective in animals. Laboratory and animal studies are done before a substance is tested in people.
Laboratory and animal studies have tested the effects of cannabinoids in laboratory experiments. See the Laboratory/Animal/Preclinical Studies section of the health professional version of Cannabis and Cannabinoids for information on laboratory and animal studies done using cannabinoids.
Have any studies of Cannabis or cannabinoids been done in people?
No ongoing studies of Cannabis as a treatment for cancer in people have been found in the CAM on PubMed database maintained by the National Institutes of Health.
Small studies have been done, but the results have not been reported or suggest a need for larger studies.
- Cannabidiol (CBD) taken by mouth to treat solid tumors that have recurred (come back).
- An oral spray combining 2 cannabinoids (delta-9-THC and CBD) given with temozolomide to treat recurrent glioblastoma multiforme.
- CBD taken by mouth to treat acute graft-versus-host disease in patients who have undergone allogeneic hematopoietic stem cell transplantation.
Cannabis and cannabinoids have been studied as ways to manage side effects of cancer and cancer therapies.
Nausea and vomiting
Cannabis and cannabinoids have been studied in the treatment of nausea and vomiting caused by cancer or cancer treatment:
- Delta-9-THC taken by mouth: Two cannabinoid drugs, dronabinol and nabilone, approved by the U.S. Food and Drug Administration (FDA), are given to treat nausea and vomiting caused by chemotherapy in patients who have not responded to standard antiemetic therapy. Clinical trials have shown that both dronabinol and nabilone work as well as or better than other drugs to relieve nausea and vomiting.
- Oral spray with delta-9-THC and CBD: Nabiximols, a Cannabis extract given as a mouth spray, was shown in a small randomized, placebo-controlled, double-blinded clinical trial in Spain to treat nausea and vomiting caused by chemotherapy.
- Inhaled Cannabis: Ten small trials have studied inhaled Cannabis for the treatment of nausea and vomiting caused by chemotherapy.
Newer drugs given for nausea caused by chemotherapy have not been directly compared with Cannabis or cannabinoids in cancer patients.
There is growing interest in treating children for symptoms such as nausea with Cannabis and cannabinoids, but studies are limited. The American Academy of Pediatrics has not endorsed Cannabis and cannabinoid use because of concerns about its effect on brain development.
Stimulating appetite
The ability of cannabinoids to increase appetite has been studied:
- Delta-9-THC taken by mouth: A clinical trial compared delta-9-THC (dronabinol) and a standard drug (megestrol, an appetite stimulant) in patients with advanced cancer and loss of appetite. Results showed that delta-9-THC did not help increase appetite or weight gain in advanced cancer patients compared with megestrol. However, a clinical trial of patients with HIV /AIDS and weight loss found that those who took delta-9-THC had better appetite and stopped losing weight compared with patients who took a placebo.
- Inhaled Cannabis: There are no published studies of the effect of inhaled Cannabis on cancer patients with loss of appetite.
Pain relief
Cannabis and cannabinoids have been studied in the treatment of pain:
- Vaporized Cannabis with opioids: In a study of 21 patients with chronic pain, vaporized Cannabis given with morphine relieved pain better than morphine alone, while vaporized Cannabis given with oxycodone did not give greater pain relief. Further studies are needed.
- Inhaled Cannabis: Randomized controlled trials of inhaled Cannabis in patients with peripheral neuropathy or other nerve pain found pain was reduced in patients who received inhaled Cannabis compared with those who received placebo.
- Cannabis plant extract: A study of Cannabis extract that was sprayed under the tongue found it helped patients with advanced cancer whose pain was not relieved by strong opioids alone. In another study, patients who were given lower doses of cannabinoid spray showed better pain control and less sleep loss than patients who received a placebo. Control of cancer-related pain in some patients was better without the need for higher doses of Cannabis extract spray or higher doses of their other pain medicines. Adverse events were related to high doses of cannabinoid spray.
- Delta-9-THC taken by mouth: Two small clinical trials of oral delta-9-THC showed that it relieved cancer pain. In the first study, patients had good pain relief, less nausea and vomiting, and better appetite. A second study showed that delta-9-THC could relieve pain as well as codeine. An observational study of nabilone also showed that it relieved cancer pain along with nausea, anxiety, and distress when compared with no treatment. Neither dronabinol nor nabilone is approved by the FDA for pain relief.
Anxiety
Cannabis and cannabinoids have been studied in the treatment of anxiety.
- Inhaled Cannabis: A small case series found that patients who inhaled Cannabis had improved mood, improved sense of well-being, and less anxiety. In another study, 74 patients newly diagnosed with head and neck cancer who were Cannabis users were matched to 74 nonusers. The Cannabis users had markedly lower anxiety or depression and less pain or discomfort than the nonusers. The Cannabis users were also less tired, had more appetite, and reported greater feelings of well-being.
Have any side effects or risks been reported from Cannabis and cannabinoids?
Side effects of cannabinoids can include:
- Fast heartbeat.
- Low blood pressure.
- Muscle relaxation.
- Bloodshot eyes.
- Slowed digestion.
- Dizziness.
- Drowsiness.
- Depression.
- Hallucinations.
- Paranoia.
Both Cannabis and cannabinoids may be addictive. Symptoms of withdrawal from cannabinoids include:
- Being easily annoyed or angered.
- Trouble sleeping.
- Unable to stay still.
- Hot flashes.
- Nausea and cramping (rare).
These symptoms are mild compared with symptoms of withdrawal from opiates and usually go away after a few days.
Studies on risks from Cannabis use
Studies on the risk of various cancers linked to Cannabis smoking have shown the following:
- Lung cancer: Because Cannabis smoke contains many of the same substances as tobacco smoke, there are concerns about how inhaled Cannabis affects the lungs. A cohort study of men in Africa found that there was an increased risk of lung cancer in tobacco smokers who also inhaled Cannabis. A population study of lung cancer patients found that low Cannabis use was not linked to an increased risk of lung cancer or other aerodigestive tract cancers.
- Testicular cancer: A 1970 study interviewed over 49,000 Swedish men aged 19 to 21 years about their personal history of using Cannabis at the time they enlisted in the military and then followed them for up to 42 years. The study did not find a link between those who had “ever” used Cannabis and testicular cancer, but did find that “heavy” use of Cannabis (more than 50 times in a lifetime) was linked to more than twice the risk of testicular cancer. The study was limited by the way data was gathered and did not note whether the testicular cancers were seminoma or nonseminoma types or whether Cannabis use also occurred after enlistment.
- Bladder cancer: A review of bladder cancer rates in Cannabis users and non-users was done in over 84,000 men who took part in the California Men’s Health Study. After more than 16 years of follow-up and adjusting for age, race, ethnic group, and body mass index, rates of bladder cancer were found to be 45% lower in Cannabis users than in men who did not report Cannabis use.
Larger studies that follow patients over time are needed to find if there is a link between Cannabis use and a higher risk of testicular germ cell tumors.
Are Cannabis or cannabinoids approved by the U.S. Food and Drug Administration for use as a cancer treatment or treatment for cancer-related symptoms or side effects of cancer therapy?
The U.S. Food and Drug Administration (FDA) has not approved Cannabis or cannabinoids for use as a cancer treatment.
Cannabis is not approved by the FDA for the treatment of any cancer-related symptom or side effect of cancer therapy.
Two cannabinoids (dronabinol and nabilone) are approved by the FDA for the treatment of nausea and vomiting caused by chemotherapy in patients who have not responded to antiemetic therapy.