EducationA full guide to medical cannabis and cancer

A full guide to medical cannabis and cancer

13 min read

Sam North

A full guide to medical cannabis and cancer


As public interest in medical cannabis continues to grow, so does the number of people intrigued by its potential medical benefits. However, the abundance of information available online can often leave the general public perplexed, even frustrated, particularly when it comes to understanding cannabis as a potential complementary treatment option for cancer.

This article aims to provide you with all the vital information you need to know about the intersection of medicinal cannabis and cancer, presented in a clear, concise, and comprehensive manner.

But, before we go any further, we must make one point crystal clear. Currently, there is zero evidence supporting the idea that cannabis can cure cancer. In this article, we will review the current clinical data pertaining to medicinal cannabis administration for cancer patients. Also, we will discuss the potential of cannabis to reduce the symptoms and side effects relating to conventional cancer treatment options.

Cancer is a dreaded, sometimes fatal disease caused by dividing cells that spread to surrounding tissues. Cancer manifests in a vast array of types and varying degrees of severity, posing considerable challenges in terms of diagnosis and subsequent treatment. Traditional approaches encompass surgical intervention, radiation therapy, and chemotherapy. However, the combined effects of these treatments can present significant side effects, imposing additional hardships on the patient and their loved ones.

That’s why many people are turning to complementary treatment options, such as medicinal cannabis, in hopes of reducing their symptoms. There is a growing body of evidence that suggests that cannabinoids may have some anti-tumour properties, but the science is not yet conclusive. They have also been shown to help ease the burden that conventional therapy options place on the body and mind. 

In today's article, we’ll go over how this plant affects your body, cancer cells, its potential benefits, how to use it, and its side effects. Furthermore, we’ll highlight recent cannabis cancer studies that have shown great promise. 

How cannabis affects your body

Before we dive into the effects and potential benefits of the cannabis plant, you have to understand how it impacts your body. Recent studies have started exploring the importance of the endocannabinoid system found in all animals, humans included.

Also known as ECS, this network of receptors (CB1 and CB2) and signalling compounds (endocannabinoids) help to regulate numerous critical body functions. This includes:

  • Temperature control
  • Sleep regulation
  • Emotional processing
  • Inflammatory and immune responses
  • Pain control
  • Ability to learn and memorise
  • Sexual function

Having this in mind, the two cannabinoid receptors play a key role in studies. The CB1 receptors outnumber many other brain receptors, and they are stimulated by the endocannabinoid molecules our bodies naturally produce.

The structure of these endocannabinoids is remarkably similar to the ones found in the cannabis plant (phytocannabinoids). This is thought to be the reason cannabis has the ability to influence the activity of receptors, which can impact a range of physical responses. Stimulating these receptors can also lead to the psychotropic effect expected from cannabis that contains elevated levels of THC.

The CB2 receptors, on the other hand, mainly affect our immune functioning system since they’re mostly found in the immune tissues.

The effect of different cannabinoids

Before delving further into the potential advantages of medicinal cannabis for cancer patients, it is crucial to acknowledge that various cannabinoids exert distinct effects on our bodies. Even though there are 113 phytocannabinoids (cannabinoids produced by cannabis) that have so far been isolated from cannabis, there are two phytocannabinoids that studies have focused on – THC and CBD.

Studies show that both might offer the possibility of positive outcomes for cancer patients. They interact with the ECS receptors (along with other internal systems) and have the ability to modulate how these systems function. 


Delta-9-tetrahydrocannabinol, also known as THC, has a similar structure to the anandamide endocannabinoid. Since THC interacts with the CB1 receptors, people who consume it might experience a euphoric high feeling. Studies have shown that there are both potential benefits and side effects from it.



May reduce nausea

Altered sense of time

May reduce pain

Slowed reaction time

Stimulates appetite

Loss of balance and coordination

Impaired memory


The second significant cannabinoid produced by cannabis (and hemp) plants is cannabidiol, or CBD. Unlike THC, CBD does not produce any intoxicating effects.

Even though there’s an ever-present need for ongoing research about exactly how CBD interacts with the body, studies have shown that CBD might interact with the 5-HT1A serotonin receptor and the TRPV1 vanilloid receptor. Due to these interactions, many patients have experienced antianxiety and pain-reducing effects after taking CBD.

It has also shown to have a weak affinity to both the CB1 and CB2 receptors, and to slow the enzymatic breakdown of our own endocannabinoids, thereby increasing their concentration. Knowing this, it’s no surprise that CBD could have a range of potential benefits for a vast range of health issues.

Cannabis and cancer therapy

When considering the impact of cannabis on cancer treatment, it is crucial to acknowledge the limited availability of peer-reviewed research to substantiate definitive claims. The majority of experiments have been conducted on animals within controlled laboratory environments. Prior to pursuing any alternative medicine options, it is advisable to consult a medical professional to ensure well-informed decision-making regarding your treatment choices.

However, when a patient is already undergoing the required doctor-prescribed therapy, such as chemotherapy, cannabis offers several potential benefits, along with some possible drawbacks.

Potential benefits

There are numerous studies focusing on medicinal cannabis and cancer that we can look at to see what potential benefits may be on the counter for cancer sufferers. These studies point out three main symptom-reducing benefits - 

  • Reducing nausea and vomiting
  • Pain relief
  • Improving appetite

Reducing nausea and vomiting

Chemotherapy-induced nausea and vomiting are among the most common unwanted effects of cancer treatment. More than 80% of cancer patients experience this side effect, which leads to other potential health risks. Furthermore, there’s a strict diet that is usually followed to lessen the symptoms, including:

  • Eating bland and room-temperature food
  • Avoiding sweet, spicy, or fried food
  • Eating small meals with a high caloric value

A study from 2019, which included cancer patients undergoing medical cannabis treatment through a four-month period, showed that nausea and vomiting symptoms were reduced in 50% of the participants. Additionally, the therapy was well tolerated by most of the patients and led to lasting and meaningful improvements.

There are three common methods of administration when taking medical cannabis to reduce nausea and vomiting:

  • Cannabis inhalation
  • THC and CBD oral spray or drops
  • Edible medical cannabis products

Pain relief

Pain and cancer treatment unfortunately often go hand-in-hand. This pain can occur during chemotherapy or radiation treatment and can prevent the patient from being able to lead a normal, pain-free life. 

Recent studies show that the application of cannabis may lead to pain relief in patients experiencing negative side effects from opioid analgesics. Researchers suggest significant improvements by reviewing five studies surrounding the effect of THC and CBD in cancer-related pain treatment. However, some side effects registered were hypotension, mental clouding, drowsiness, and vomiting.

Improving appetite

Another potential side effect of cancer treatment is the loss of appetite. Many patients even experience changes in the way the food smells or tastes. Moreover, drinking plenty of fluids, staying active, and having a healthy diet are invaluable when undergoing cancer treatment.

Even though it may sound less significant than the other side effects, the loss of appetite can lead to ‘cancer cachexia’ syndrome. This occurs in over 80% of advanced-cancer patients and results in severe weight and muscle loss.

A study published in 2019 indicates that 17.6% of the participants who consumed 5 mg cannabis capsules demonstrated a significant weight increase. Even though there weren’t any visible side effects, the researchers concluded that further studies were needed before any factual claims could be made regarding the efficacy of medicinal cannabis and the improvement of appetite. 

Other potential benefits

Despite the three most commonly reported benefits of using medical cannabis for cancer patients aim to reduce the side effects of certain traditional treatments, studies show that it may help with several other cancer-related issues. Some of them are chemotherapy-induced peripheral neuropathy, gastrointestinal distress, anxiety, and sleep disorders.

Potential drawbacks

The potential drawbacks of medicinal cannabis depend on the type of cannabinoids being administered. To better grasp the adverse effects, it’s important to understand both the plant’s side effects and how it may react with ongoing cancer treatment.

Cannabis-related side effects

Some potential side effects caused by medical cannabis use may include:

  • Drowsiness and dizziness – this can be caused due to a sudden drop in blood pressure and cerebral blood flow.
  • Bloodshot eyes – vasodilation, when the blood vessels in the eyes expand and appear red, is a common side effect.
  • Muscle relaxation – known as a natural muscle relaxant, cannabis inhibits the release of neurotransmitters that induce muscle rigidity.
  • Heart arrhythmia or tachycardia – by increasing the sympathetic activity and reducing the parasympathetic activity, cannabis can increase the overall cardiac output.
  • Slow digestion – cannabis slows down bowel movement and decreases gastric-acid production.

As far as the potential cancer-treatment drawbacks related to medical cannabis use, it’s essential to note that different adverse effects might occur depending on the cancer type. However, some of the more serious side effects include:

  • Damage to crucial blood vessel cells – some studies show that high doses of THC may lead to harm to the CVS, such as coronary vasospasms, platelet aggregation, and peripheral arteritis.
  • Further encouraging cancer cell growth – depending on the type of cancer, a study from 2004 shows that some cannabinoids, such as THC, may accelerate the proliferation of cancer cells. This may only result in cancer spreading faster.

Interactions with cancer treatment

The interaction of medical cannabis and other treatments for cancer can create unexpected reactions. Some patients may experience an increased risk of bleeding when combining cannabis with anticoagulants or antiplatelet medications.

Moreover, these interactions can depend on the type and dosage of cannabinoid used. Therefore, caution is necessary to avoid any severe side effects.

Cannabis cancer studies

Now that we’ve gone over the potential benefits and drawbacks, there are several significant cannabis cancer studies we can look at.

Studies on the endocannabinoid system and cannabis application

A recent study on the endocannabinoid system shows that cannabis-based therapies may have potential benefits in numerous cases. Therefore, THC and CBD-based medicine show promise in reducing the severity or helping treat:

  • Nausea
  • Chronic pain
  • Sleeping disorders
  • Epilepsy

However, since the ECS system affects the body’s metabolism, neurological system, and overall homeostasis, further research is needed before any conclusions are made.

Studies on colon cancer and cannabinoid therapy

There are three important publications related to colon cancer. The first one, published in 2005, shows that the anandamide targets cells with COX-2 inhibitors and may eliminate tumour cells.

In the next study, this time from 2007, they discuss the potential anticancer agents of THC when interacting with the CB1 receptor. THC has been shown to have the potential to regulate signalling pathways, and so it may play a key role in cell survival and growth. A 2010 study implies that anandamide can induce cell death in apoptosis-resistant cancer cells.

The latest study, published in 2021, may further show the potential effectiveness of cannabis extracts against colon cancer. Since the compounds seem to be able to target the signalling pathways of cancer development, they can potentially be used as therapy. Furthermore, their administration may lead to dose reductions of other more toxic drugs used as treatment, therefore reducing unwanted side effects.

Studies on skin cancer and cannabis therapy

A recent 2020 research paper indicated that six eligible studies had proven that certain individual or combined cannabinoids could be effective in apoptosis and autophagy in melanoma cells. Furthermore, they also showed that these compounds might reduce tumour growth.

Another study from 2019 also showed that CBD has the potential to possibly reduce tumour size in mice subjects when compared with the control group, and that the therapeutic effect of cannabinoids might be used to influence the course of melanoma.

Studies on lung cancer and cannabis use

Even though the above-mentioned studies showed potential benefits of using cannabis, lung cancer studies show possible risks.

Based on a 2008 study, researchers found that long-term cannabis usage may lead to lung cancer. The theory here is that it is the combustion and then inhalation of the cannabis flower that could lead to this increase in rates of lung cancer.

This only highlights just how important it is to consult with a medical professional before considering alternative treatment options.

Legal regulations and safety measures

Even though the medical application of cannabis was legalised on 1 November 2018, it’s still illegal to possess, grow, and distribute it in the UK. 

While there are numerous rules and regulations surrounding medicinal cannabis prescription and administration, the path for patients to access medicinal cannabis is now clear. As long as you have been diagnosed with one of the conditions or diseases that have been approved for medicinal cannabis treatment, a specialist doctor will be able to legally provide you with a prescription. 

Never buy cannabis-based products from unreliable sources. The current consumer market is flooded with unregulated cannabis products. Always make sure that your medicinal cannabis is prescribed by a qualified and registered physician, and that you only take the prescribed medicinal product. This will ensure the best possible health outcomes. 


Medical cannabis has the potential to help treat a variety of conditions, including cancer. It is important to understand how it works and the possible benefits and drawbacks associated with its use. There are numerous studies on the effects of medical cannabis on various types of cancer, but further research is needed in order to make definitive conclusions.

It’s also essential to understand the legal regulations surrounding medical cannabis usage and at only trusted sources for products that have been prescribed by a qualified doctor.

Releaf understands the importance of medical cannabis in treating various medical conditions. With our tailored monthly packages, specialist consultations for medical cannabis, and a unique medical cannabis card for protection, you can access the treatment you need without worrying about the stigma.

If you have any further questions about medical cannabis and cancer, don’t hesitate to contact us.

It is important to seek medical advice before starting any new treatments. The patient advisors at Releaf are available to provide expert advice and support. Alternatively, click here to book a consultation with one of our specialist doctors.

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Sam North, a seasoned writer with over five years' experience and expertise in medicinal cannabis, brings clarity to complex concepts, focusing on education and informed use.

medically reviewed

Our articles are written by experts and reviewed by medical professionals or compliance specialists. Adhering to stringent sourcing guidelines, we reference peer-reviewed studies and scholarly research. View our editorial policy.

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