Cannabis is often portrayed as a miracle plant, providing healing solutions for almost every affliction known to man. While it’s true that compounds found in cannabis have a therapeutic reach far broader than almost any other botanical substance in nature, it’s unrealistic to suggest that it is suitable for every health condition. Especially when we consider how little is really known about its interaction with our body’s immune system.

When it comes to the immune system and cannabis, most research has been carried out into the effects of the plant’s two principal cannabinoids, THC and CBD. They have been termed immunomodulators, meaning they change the action of the immune system. Scientists have observed that both tend to dampen rather than strengthen the immune system, eliciting an anti-inflammatory effect. This has made the use of cannabinoids of particular interest in diseases where there is too much immune activity or excessive inflammation, as in the cases of autoimmune and neurodegenerative diseases.

But what happens if you regularly take cannabis and have a condition where your immunity is compromised such as HIV, or you are fighting off a viral or bacterial infection? Is it ok to take cannabis in these instances?

Our Immune System – an overview

To try and find an answer, let’s first get a basic understanding of how our immune system works.

In life we are constantly exposed to infectious diseases, bacteria and viruses (antigens) all intent on running amok and wreaking havoc. Thank heavens then we have an immune system, designed to protect us from these outside invaders, otherwise frankly, we’d be dead.

A key player in the immune system’s arsenal are white blood cells or leukocytes which seek out and destroy any unwanted visitors. Leukocytes are divided into two groups: lymphocytes (B cells and T cells) which destroy antigens as well as helping the body to remember previous attackers, and phagocytes which literally eat up and consume foreign intruders.

Many of us are familiar with the term T Cells as these are the immune cells wiped out by the HIV virus, making sufferers vulnerable to normally harmless infections which in the absence of T cells can become life threatening.

In short, our immune system is a tremendously complex network of cells, tissues and organs, normally running with military precision in order to keep us healthy. And intrinsically linked to keeping this fine balance is the body’s endocannabinoid system.

Relationship Between the Endocannabinoid and Immune System

Discovered as recently as the 1990s, ever since the endocannabinoid system has been shedding new light on how our bodies function. Comprising G protein coupled receptors and cannabis-like chemicals called endocannabinoids, its modus operandi is to maintain the body in a state of balance or homeostasis. In the context of the immune system, it’s the CB2 receptors that are of most interest as they outnumber the CB1 receptors by 100 to 1. The activation of the CB2 receptor creates an anti-inflammatory effect and is consequently a therapeutic target for research into autoimmune disorders and neurodegenerative disease.

Immune cells themselves not only have endocannabinoid receptors, but also make, transport and breakdown endocannabinoids. Scientists even go as far a to suggest that our immune function is controlled by the endocannabinoid system, not only in terms of suppressing its action when it becomes over-activated, but also stimulating it when it is weakened.

Scientists know that introducing plant cannabinoids like THC and CBD into the body has a direct impact on the endocannabinoid system and in turn our health. It makes sense then that consuming medical cannabis will also directly impact our immune system. But what researchers are struggling to understand is exactly how.

Cannabinoids and the Immune System

Until now, most research into cannabinoids and the immune system has been carried out on THC, the psychoactive and most abundant compound in cannabis. THC activates both the CB1 and CB2 receptors, mimicking the action of the body’s own endocannabinoids, Anandamide and 2-AG, which tend to have an overall immunosuppressive effect.

A study in 2003 on guinea pigs that had been infected with the herpes virus found that when administered THC, the virus took hold quicker and recurred more frequently. Another investigation carried out on mice infected with the flu, found that THC increased the spread of the virus due to a reduced the amount of T-cells in the lungs, all of which suggest that THC suppresses the immune system.


But things get a whole lot more interesting when we introduce THC’s effect on HIV into the mix. Until recently, preclinical research had corroborated the view that THC worsened the disease, increasing viral load.

THC has been used as a palliative treatment by HIV patients for some time due to its ability to improve appetite, reduce anxiety and ease pain. But recent research takes THC’s role even further, suggesting it can actually undo some of the damage caused to the immune system by the disease.


In 2011 a ground breaking paper was published in which the effects of THC was studied on monkeys with the simian version of HIV, SIV. 28 days prior to being injected with the virus, the subjects were given THC on a daily basis. Lead scientist Dr Molina and her team discovered that THC appeared to have some kind of protective effect, lengthening the lives of the monkeys and reducing the viral load. Subsequent research published by Molina in 2014 in which THC was given to monkeys over 17 months prior to infection, confirmed earlier findings whereby there was less intestinal damage caused by the virus, an increase in T-cells, and a decrease in viral load.

These surprising results have recently been replicated in humans in an study conducted by scientists at Virginia State and Florida Universities. The white blood cell counts were compared in a sample of 95 HIV patients, some of which were chronic cannabis users. Scientists discovered that the CD4 and CD8 counts were higher in patients using cannabis, suggesting that their immune systems had been bolstered by the plant. A limitation to the study, however, is the lack of data about the cannabinoid content of the cannabis consumed.

CBD and the Immune System

CBD, the non-psychoactive cannabinoid has been much lauded of late for its anti-inflammatory action. Inflammation is part of the immune response and is vital to the healing process. However, in excess, inflammation can be a sign of a malfunctioning immune system and is linked to autoimmune and neurodegenerative diseases. In preclinical studies, CBD has been found to reduce inflammation in animal models and many patients testify that it eases the symptoms related to chronic inflammation in conditions such as rheumatoid arthritis and inflammatory bowel disease. All of which suggests that CBD has an immunosuppressant effect on the body.

Unlike THC, CBD has little affinity with the CB1 and CB2 receptors, but scientists have observed that the compound suppresses T cell function, the type of white blood cells responsible for attacking foreign substances and stimulating antibody production. So it is possible that taking CBD when your immune system needs to be working at full force, might just be counterproductive.

Take for instance when you have a common cold or the flu. On the one hand, it would be tempting to take CBD for the annoying aches and pains associated with a flu virus. In the past, how many of us have reached for an ibuprofen, the over the counter anti-inflammatory medication, to get rid of that headache or sinus pain? But sometimes, these painful unpleasantries are signs of the body’s immune system doing its job and suppressing this activity might not pay off in the long run.

A study comparing ibuprofen with paracetamol showed that subjects who had taken the anti-inflammatory medication, were more likely to come back with worsening or new symptoms, compared to those who had taken just paracetamol. Professor Little, the lead researcher said: “This may have something to do with the fact the ibuprofen is an anti-inflammatory. It is possible that the drug is interfering with an important part of the immune response.”

While ibuprofen and CBD are clearly two very different animals, the same principle might just apply.

Cannabinoids, Cancer and the Immune System

With this tendency of cannabinoids to dampen the immune response, it could make one reconsider their use in cases of cancer.

Medical cannabis is used palliatively by many people worldwide to cope with the debilitating side effects of cancer treatments like chemotherapy. But a growing number of cancer patients are taking inspiration from the preclinical studies performed in scientific laboratories showing the cannabis plant also elicits antitumoral effects. (2)

The onset of cancer can occur due a number of reasons, but a key factor can be a compromised immune system. Apoptosis or programmed cell death is an integral immune system action. Malfunctioning of the immune system may lead to increased or decreased cell death – increased cell death being an autoimmune disease, and decreased cell death, cancer.

Indeed, cancer cells are unique in that they somehow manage to evade all natural processes by which cells normally commit suicide, leading to tumor development and resistance to therapy.

This is where THC comes in. In pioneering research at the Complutense University in Madrid, scientists discovered that THC causes apoptosis in cancer cells. But curiously enough, THC also causes cell death in lymphocyte cells as part of its immunosuppressive action. However, in most cases the antitumoral action of THC is greater than the inhibitory effect on the immune system, with scientists looking for a therapeutic balance between the two actions.

But in some instances, THC’s dampening effect on the immune system can have a negative effect in cancer treatment. In a study conducted at the Rambam Medical Centre in Haifa, Israel, patients taking medical cannabis alongside the immunotherapy cancer drug Opdivo showed “a greatly reduced response to the drug,” although no significant change in overall survival rates for patients was noted.

So where does this leave patients in practical terms who are considering taking medical cannabis?

Much research needs to be undertaken not just in preclinical trials, but on humans. I spoke to Dr Mariano Garcia de Palau, a Spanish medical cannabis doctor who is member of the Spanish Medical Cannabis Observatory, to see how a practicing physician views the complex relation between cannabis and the immune system.

“I believe it (cannabis) is immunosuppressive when there is hyper-immune response,” says Dr Garcia de Palau, “but otherwise it regulates and corrects the immune system. In fact you could say it functions like the endocannabinoid system, bringing equilibrium to the organism. I’ve never experienced problems in this sense.”

So what should you do if you have a compromised immune system and are not sure if medical cannabis is appropriate for you? Always where possible consult with your medical practitioner, particularly if you live in a part of the world where medical cannabis is integrated into the health system. In the meantime, we can only hope that more research emerges further clarifying the complex relationship between the endocannabinoid system, our immune response, and compounds in the cannabis plant.



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