Cannabis oil and cancer
Find out about cannabis, cannabis oil, CBD oil and cancer, including the difference between THC and CBD.
What is cannabis?
Cannabis is a plant. It produces a resin that contains different substances. Some of these may have medicinal value. These substances are called cannabinoids.
2 of the main cannabinoids tested in medicines are:
- THC (delta-9-tetrahydrocannabidiol)
- CBD (cannabidiol).
THC is a psychoactive substance. This means it can affect your mood and how you feel so that you feel ‘high’ or ‘stoned’. CBD does not cause these effects.
You have probably heard many names for cannabis. These include marijuana, hemp, pot, grass and hash. Cannabis has been used both medicinally and recreationally for thousands of years.
Different types of cannabis contain different amounts of THC and CBD. For example, hemp comes from a cannabis plant that contains only a very small amount of THC. Hemp oil is used as a food supplement and in products like soaps.
Cannabis and the law
Cannabis is classified as a class B drug in the UK. This means it is illegal to have it or sell it. The laws about cannabis mean that:
- THC and products that contain THC are illegal in the UK
- selling or possessing CBD is legal.
Cannabis and medicines
There are some medicines available in the UK that come from cannabis. These include:
- Sativex®, which is used to treat multiple sclerosis
- Nabilone®, which is used to relieve sickness caused by chemotherapy.
These medicines go through a process to make sure they are safe to be licensed in the UK. This is the same process that is used to decide whether any medicine can be prescribed in the UK.
Medicinal cannabis (also called cannabis-based products for medicinal use) was legalised in the UK in November 2018. This means these specific medicines can be prescribed by specialist doctors for certain medical conditions. These conditions include rare, severe forms of epilepsy and severe spasticity (muscle stiffness and spasms) caused by multiple sclerosis. Medicinal cannabis cannot currently be prescribed for cancer or pain.
The National Institute for Health and Care Excellence (NICE) has a list of the medical conditions where cannabis-based products for medicinal use may be prescribed.
Cannabis and cancer
There is a lot of interest in the possible effects of cannabinoids on cancer.
Scientists have researched THC and CBD to see if they could have any role in the treatment of cancer. Most of this research has been done in the laboratory. There have also been some small studies in people. Research continues to find out if cannabis-based medicines could help in the treatment of some cancers or cancer symptoms.
So far, different cannabinoids seem to have different effects on different types of cancer. At the moment, there is no reliable medical evidence to show whether cannabis, in any form, can effectively and safely treat cancer in humans.
What does the research say?
Research has found that cannabinoids can:
- cause a cell to die
- stop cells from dividing
- stop cells from developing new blood vessels.
But it has also found that cannabinoids can:
- damage important blood vessels
- encourage cancer cells to grow in some situations
- make the immune system less effective – the immune system fights diseases such as cancer.
It is possible that cannabis may have an effect in treating some types of cancer. But it may make other types of cancer grow or spread more quickly.
Research has also looked at how using cannabis may affect the risk of developing cancer. This has produced different results. It is also harder to study, as cannabis is often mixed with tobacco, which increases a person’s risk of cancer. Because of these mixed results, experts feel there needs to be more research into the chemicals found in cannabis and their possible benefits.
Cannabinoids may help relieve some symptoms of cancer, for example pain and feeling sick. It may also help with side effects of treatment. But more research is needed to learn about the types of cannabinoid and the doses needed.
Cannabis oil and CBD oil
Many types of cannabis oil are available online. Cannabis oil can contain different amounts of THC and CBD.
CBD oil is also sold in some shops, such as health food shops. It can be sold in the UK as a food supplement, if the seller does not make any claims about its medicinal properties.
CBD oil in its pure form does not contain THC. This means it does not have any psychoactive effects (it does not make you feel stoned).
CBD oil is not a controlled substance under the Misuse of Drugs Act. The Food Standards Agency advises that healthy adults should limit their CBD intake to 10mg each day. This is because of concerns about the long-term consumption of CBD and its possible effects on the liver and the thyroid gland.
There are different ways of taking CBD oil. These include a liquid that you put under your tongue, or capsules that you swallow.
Understandably, many people want to try anything that may help treat cancer, particularly if conventional cancer treatments are not working well. This could be if they have cancer themselves, or if a loved one has cancer.
But if you are thinking about using CBD oil, there are some important things to consider.
Effects of CBD oil on cancer treatment
Buying cannabis products online
Buying cannabis products online, including CBD oil, can be risky. They are not regulated, so often the quality and ingredients are impossible to know.
In 2017, a researcher tested 84 CBD products sold online. The results showed that:
- about 1 in 4 (26%) contained less CBD than stated on the label
- almost half (48%) contained more CBD than stated on the label
- more than 1 in 5 (21%) contained THC.
Side effects of cannabis oil
There are side effects of using cannabis oil. THC can:
- increase your heart rate
- cause dizziness, hallucinations and paranoia
- make you feel stoned.
Effects on other medicines
CBD and THC can affect how some medicines work.
Finding reliable information online
If you are looking for information online, you need to know that it is accurate and up to date.
Here are some things to think about when you are looking at a website:
- Is the information regularly updated? You should be able to find the date when the information was last reviewed on each page.
- Is it clear who has written the information? A good website should tell you about the organisation that has made the pages or written the information.
- Are there references? The website should list the sources it used to write the information, or tell you who to contact to find out.
- Is the website sponsored by a company? If so, it might mean the information is biased towards that company’s products or services.
The National Cancer Institute (NCI) and Cancer Research UK have more detailed information about cannabis.
About our information
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer.
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References
Below is a sample of the sources used in our complementary therapies information. If you would like more information about the sources we use, please contact us at informationproductionteam@macmillan.org.uk
Balneaves LG, Watling CZ, Hayward EN, Ross B, Taylor-Brown J, Porcino A, Truant TLO. Addressing Complementary and Alternative Medicine Use Among Individuals With Cancer: An Integrative Review and Clinical Practice Guideline. J Natl Cancer Inst. 2022 Jan 11;114(1):25-37. Available from: doi: 10.1093/jnci/djab048. PMID: 33769512; PMCID: PMC8755493. [Accessed September 2023].
Integrative Medicine [Internet]. Memorial Sloan Kettering Cancer Center. 2020. Available from: www.mskcc.org/cancer-care/diagnosis-treatment/symptom-management/integrative-medicine [accessed September 2023].
NICE. Guidance on Cancer Services Improving Supportive and Palliative Care for Adults with Cancer. The Manual National Institute for Clinical Excellence [Internet]. 2019. Available from: www.nice.org.uk/guidance/csg4/resources/improving-supportive-and-palliative-care-for-adults-with-cancer-pdf-773375005 [accessed September 2023].
Overview of complementary, alternative, and integrative medicine practices in oncology care, and potential risks and harm. UpToDate. Available from: www.uptodate.com/contents/overview-of-complementary-alternative-and-integrative-medicine-practices-in-oncology-care-and-potential-risks-and-harm?source=mostViewed_widget [accessed September 2023].
Date reviewed
Our cancer information meets the PIF TICK quality mark.
This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.
The language we use
We want everyone affected by cancer to feel our information is written for them.
We want our information to be as clear as possible. To do this, we try to:
- use plain English
- explain medical words
- use short sentences
- use illustrations to explain text
- structure the information clearly
- make sure important points are clear.
We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.
You can read more about how we produce our information here.
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