Marijuana and Cancer
Marijuana is the name given to the dried buds and leaves of varieties of the Cannabis sativa plant, which can grow wild in warm and tropical climates throughout the world and be cultivated commercially. It goes by many names, including pot, grass, cannabis, weed, hemp, hash, marihuana, ganja, and dozens of others.
Marijuana has been used in herbal remedies for centuries. Scientists have identified many biologically active components in marijuana. These are called cannabinoids. The two best studied components are the chemicals delta-9-tetrahydrocannabinol (often referred to as THC), and cannabidiol (CBD). Other cannabinoids are being studied.
At this time, the US Drug Enforcement Administration (DEA) lists marijuana and its cannabinoids as Schedule I controlled substances. This means that they cannot legally be prescribed, possessed, or sold under federal law. Whole or crude marijuana (including marijuana oil or hemp oil) is not approved by the US Food and Drug Administration (FDA) for any medical use. But the use of marijuana to treat some medical conditions is legal under state laws in many states.
Dronabinol, a pharmaceutical form of THC, and a man-made cannabinoid drug called nabilone are approved by the FDA to treat some conditions.
Different compounds in marijuana have different actions in the human body. For example, delta-9-tetrahydrocannabinol (THC) seems to cause the “high” reported by marijuana users, and also can help relieve pain and nausea, reduce inflammation, and can act as an antioxidant. Cannabidiol (CBD) can help treat seizures, can reduce anxiety and paranoia, and can counteract the “high” caused by THC.
Different cultivars (strains or types) and even different crops of marijuana plants can have varying amounts of these and other active compounds. This means that marijuana can have different effects based on the strain used.
The effects of marijuana also vary depending on how marijuana compounds enter the body. The most common ways to use marijuana are in food (edible marijuana) and by smoking or vaping it (inhaled marijuana):
- Edible marijuana: When taken by mouth, such as when it’s used in cooking oils, drinks (beer, tea, vodka, soda), baked goods (biscuits, brownies, cookies), and candy, the THC is absorbed poorly and can take hours to be absorbed. Once it’s absorbed, it’s processed by the liver, which produces a second psychoactive compound (a substance that acts on the brain and changes mood or consciousness) that affects the brain differently than THC. It’s important to know that the amount of THC in foods that have had marijuana added to them is often unknown and getting to much THC might cause symptoms of overdose.
- Inhaled marijuana: When marijuana is smoked or vaporized, THC enters the bloodstream and goes to the brain quickly. The second psychoactive compound is produced in small amounts, and so has less effect. The effects of inhaled marijuana fade faster than marijuana taken by mouth.
How can marijuana affect symptoms of cancer?
A number of small studies of smoked marijuana found that it can be helpful in treating nausea and vomiting from cancer chemotherapy.
A few studies have found that inhaled (smoked or vaporized) marijuana can be helpful treatment of neuropathic pain (pain caused by damaged nerves).
Smoked marijuana has also helped improve food intake in HIV patients in studies.
There are no studies in people of the effects of marijuana oil or hemp oil.
Studies have long shown that people who took marijuana extracts in clinical trials tended to need less pain medicine.
More recently, scientists reported that THC and other cannabinoids such as CBD slow growth and/or cause death in certain types of cancer cells growing in lab dishes. Some animal studies also suggest certain cannabinoids may slow growth and reduce spread of some forms of cancer.
There have been some early clinical trials of cannabinoids in treating cancer in humans and more studies are planned. While the studies so far have shown that cannabinoids can be safe in treating cancer, they do not show that they help control or cure the disease.
Relying on marijuana alone as treatment while avoiding or delaying conventional medical care for cancer may have serious health consequences.
Possible harms of marijuana
Marijuana can also pose some harms to users. While the most common effect of marijuana is a feeling of euphoria (“high”), it also can lower the user’s control over movement, cause disorientation, and sometimes cause unpleasant thoughts or feelings of anxiety and paranoia.
Smoked marijuana delivers THC and other cannabinoids to the body, but it also delivers harmful substances to users and those close by, including many of the same substances found in tobacco smoke.
Because marijuana plants come in different strains with different levels of active compounds, it can make each user’s experience very hard to predict. The effects can also differ based on how deeply and for how long the user inhales. Likewise, the effects of ingesting marijuana orally can vary between people. Also, some chronic users can develop an unhealthy dependence on marijuana.
There are 2 chemically pure drugs based on marijuana compounds that have been approved in the US for medical use.
- Dronabinol (Marinol®) is a gelatin capsule containing delta-9-tetrahydrocannabinol (THC) that’s approved by the US Food and Drug Administration (FDA) to treat nausea and vomiting caused by cancer chemotherapy as well as weight loss and poor appetite in patients with AIDS.
- Nabilone (Cesamet®) is a synthetic cannabinoid that acts much like THC. It can be taken by mouth to treat nausea and vomiting caused by cancer chemotherapy when other drugs have not worked.
Nabiximols is a cannabinoid drug still under study in the US. It’s a mouth spray made up of a whole-plant extract with THC and cannabidiol (CBD) in an almost one to one mix. It’s available in Canada and parts of Europe to treat pain linked to cancer, as well as muscle spasms and pain from multiple sclerosis (MS). It’s not approved in the US at this time, but it’s being tested in clinical trials to see if it can help a number of conditions.
How can cannabinoid drugs affect symptoms of cancer?
Based on a number of studies, dronabinol can be helpful for reducing nausea and vomiting linked to chemotherapy.
Dronabinol has also been found to help improve food intake and prevent weight loss in patients with HIV. In studies of cancer patients, though, it wasn’t better than placebo or another drug (megestrol acetate).
Nabiximols has shown promise for helping people with cancer pain that’s unrelieved by strong pain medicines, but it hasn’t been found to be helpful in every study done. Research is still being done on this drug.
Side effects of cannabinoid drugs
Like many other drugs, the prescription cannabinoids, dronabinol and nabilone, can cause side effects and complications.
Some people have trouble with increased heart rate, decreased blood pressure (especially when standing up), dizziness or lightheadedness, and fainting. These drugs can cause drowsiness as well as mood changes or a feeling of being “high” that some people find uncomfortable. They can also worsen depression, mania, or other mental illness. Some patients taking nabilone in studies reported hallucinations. The drugs may increase some effects of sedatives, sleeping pills, or alcohol, such as sleepiness and poor coordination. Patients have also reported problems with dry mouth and trouble with recent memory.
Older patients may have more problems with side effects and are usually started on lower doses.
People who have had emotional illnesses, paranoia, or hallucinations may find their symptoms are worse when taking cannabinoid drugs.
Talk to your doctor about what you should expect when taking one of these drugs. It’s a good idea to have someone with you when you first start taking one of these drugs and after any dose changes.
What does the American Cancer Society say about the use of marijuana in people with cancer?
The American Cancer Society supports the need for more scientific research on cannabinoids for cancer patients, and recognizes the need for better and more effective therapies that can overcome the often debilitating side effects of cancer and its treatment. The Society also believes that the classification of marijuana as a Schedule I controlled substance by the US Drug Enforcement Administration imposes numerous conditions on researchers and deters scientific study of cannabinoids. Federal officials should examine options consistent with federal law for enabling more scientific study on marijuana.
Medical decisions about pain and symptom management should be made between the patient and his or her doctor, balancing evidence of benefit and harm to the patient, the patient’s preferences and values, and any laws and regulations that may apply.
The American Cancer Society Cancer Action Network (ACS CAN), the Society’s advocacy affiliate, has not taken a position on legalization of marijuana for medical purposes because of the need for more scientific research on marijuana’s potential benefits and harms. However, ACS CAN opposes the smoking or vaping of marijuana and other cannabinoids in public places because the carcinogens in marijuana smoke pose numerous health hazards to the patient and others in the patient’s presence.
Learn how marijuana and drugs derived from the marijuana plant can affect cancer-related symptoms.
General cancer information
Cannabis, CBD oil and cancer
Cannabis is a plant and a class B drug. It affects people differently. It can make you feel relaxed and chilled but it can also make you feel sick, affect your memory and make you feel lethargic. CBD oil is a chemical found in cannabis.
- Cannabis has been used for centuries recreationally and as a medicine.
- It is illegal to possess or supply cannabis as it is a class B drug.
- Research is looking at the substances in cannabis to see if it might help treat cancer.
- There are anti sickness medicines that contain man-made substances of cannabis.
What are cannabis and cannabinoids?
Cannabis is a plant. It is known by many names including marijuana, weed, hemp, grass, pot, dope, ganja and hash.
The plant produces a resin that contains a number of substances or chemicals. These are called cannabinoids. Cannabinoids can have medicinal effects on the body.
The main cannabinoids are:
- Delta-9-tetrahydrocannabinol (THC)
- Cannabidiol (CBD)
THC is a psychoactive substance that can create a ‘high’ feeling. It can affect how your brain works, changing your mood and how you feel.
CBD is a cannabinoid that may relieve pain, lower inflammation and decrease anxiety without the psychoactive ‘high’ effect of THC.
Different types of cannabis have differing amounts of these and other chemicals in them. This means they can have different effects on the body.
Cannabis is a class B drug in the UK. This means that it is illegal to have it, sell it or buy it.
CBD oil, cannabis oil and hemp oil
There are different types of oil made from parts of the cannabis plant. Some are sold legally in health food stores as a food supplement. Other types of oil are illegal.
CBD oil comes from the flowers of the cannabis plant and does not contain the psychoactive substance THC. It can be sold in the UK as a food supplement but not as a medicine. There is no evidence to support its use as a medicine.
Cannabis oil comes from the flowers, leaves and stalks of the cannabis plant. Cannabis oil often contains high levels of the psychoactive ingredient THC. Cannabis oil is illegal in the UK.
Hemp oil comes from the seeds of a type of cannabis plant that doesn’t contain the main psychoactive ingredient THC. Hemp seed oil is used for various purposes including as a protein supplement for food, a wood varnish and an ingredient in soaps.
Why people with cancer use it
Cannabis has been used medicinally and recreationally for hundreds of years.
There has been a lot of interest into whether cannabinoids might be useful as a cancer treatment. The scientific research done so far has been laboratory research, with mixed results, so we do not know if cannabinoids can treat cancer in people.
Results have shown that different cannabinoids can:
- cause cell death
- block cell growth
- stop the development of blood vessels – needed for tumours to grow
- reduce inflammation
- reduce the ability of cancers to spread
Scientists also discovered that cannabinoids can:
- sometimes encourage cancer cells to grow
- cause damage to blood vessels
Cannabinoids have helped with sickness and pain in some people.
This means a cannabis based product used to relieve symptoms.
Some cannabis based products are available on prescription as medicinal cannabis. The following medicines are sometimes prescribed to help relieve symptoms.
Nabilone is a drug developed from cannabis. It is licensed for treating severe sickness from chemotherapy that is not controlled by other anti sickness drugs. It is a capsule that you swallow whole.
Sativex is a cannabis-based medicine. It is licensed in the UK for people with Multiple Sclerosis muscle spasticity that hasn’t improved with other treatments. Sativex is a liquid that you spray into your mouth.
Researchers are looking into Sativex as a treatment for cancer related symptoms.
How you have it
Cannabis products can be smoked, vaporized, ingested (eating or drinking), absorbed through the skin (in a patch) or as a cream or spray.
CBD oil comes as a liquid or in capsules.
Prescription drugs such as Nabilone can cause side effects. This can include:
- increased heart rate
- blood pressure problems
- mood changes
- memory problems
Cannabis that contains high levels of THC can cause panic attacks, hallucinations and paranoia.
There are also many cannabis based products available online without a prescription. The quality of these products can vary. It is impossible to know what substances they might contain. They could potentially be harmful to your health and may be illegal.
Research into cannabinoids and cancer
We need more research to know if cannabis or the chemicals in it can treat cancer.
Clinical trials need to be done in large numbers where some patients have the drug and some don’t. Then you can compare how well the treatment works.
Many of the studies done so far have been small and in the laboratory. There have been a few studies involving people with cancer.
There are trials looking at whether Sativex can help with cancer pain that has not responded to other painkillers.
The results of one trial showed that Sativex did not improve pain levels. You can read the results of the trial on our clinical trials website.
Cancer nausea and vomiting
A cannabis based medicine, Nabilone, is a treatment for nausea and vomiting.
A Cochrane review in 2015 looked at all the research available looking into cannabis based medicine as a treatment for nausea and sickness in people having chemotherapy for cancer. It reported that many of the studies were too small or not well run to be able to say how well these medicines work. They say that they may be useful if all other medicines are not working.
A drug called dexanabinol which is a man made form of a chemical similar to that found in cannabis has been trialled in a phase 1 trial. This is an early trial that tries to work out whether or not the drug works in humans, what the correct dose is and what the side effects might be. The results are not available yet. You can read about the trial on our clinical trials database.
Word of caution
Cannabis is a class B drug and illegal in the UK.
There are internet scams where people offer to sell cannabis preparations to people with cancer. There is no knowing what the ingredients are in these products and they could harm your health.
Some of these scammers trick cancer patients into buying ‘cannabis oil’ which they then never receive.
You could talk with your cancer specialist about the possibility of joining a clinical trial. Trials can give access to new drugs in a safe and monitored environment.
The science blog on our website has more information about cannabis and cancer.
Cannabis is a plant and a class B drug. CBD oil is a chemical found in cannabis. Research is looking at the substances in cannabis to see if it might help treat cancer.