How Does Cannabis Affect the Immune System?

We wouldn’t last very long without our immune system. We’re constantly surrounded by bacteria, fungi, and viruses that would jump at the chance to access the resources within our cells. Our immune system comprises numerous organs, cell types, and proteins that provide several lines of defence against these external threats. However, they aren’t always enough to stamp out an infection before it takes hold. We all encounter colds, flu, and other infectious illnesses every now and then, but the genius of our immune system ensures that we’re better equipped to deal with them next time.

In order to reduce the likelihood of getting sick, many people look for ways to boost or modify their immune system through nutrition, exercise, lifestyle adjustments, and supplements. While science supports some of these strategies, others are treated with more scepticism. But where does cannabis autumn on this spectrum? Can the herb help to bolster our cellular defences and prevent or minimise infections? Or does it make matters worse? Below, we explore these questions and more.

How the Immune System Works

Before we get into how cannabis could impact immunity, let’s quickly cover how the immune system works. Our physiological defences feature two primary categories: innate immunity and adaptive immunity.

We are all born with an innate (or general) immune system that serves as the first line of defence against pathogens entering the body. It comprises barriers such as the skin and the mucous membranes (the inner lining of the nose, mouth, lungs, and other organs and cavities) that physically prevent the movement of pesky germs.

These biological walls also harness enzymes, acids, and mucus to discourage the formation of bacteria and viruses. Scavenger cells known as phagocytes also make up the innate immune system. “Phago” stems from the Greek “phagein”, which means “to consume”. Phagocytes live up to their name by enveloping and “eating” intruding pathogens.

Whereas our innate immunity uses a scattershot and unselective strategy to destroy invaders, our adaptive (or acquired) immunity works much more specifically to tackle intruders. If our innate defences fail, the adaptive immune system arrives as backup and begins to identify the pathogen and create specific antibodies designed to kill it.

Below are the two main players involved in this process:

Cannabis, the Endocannabinoid System, and Immunity

The immune system doesn't work in isolation—nothing in the body does. If you know a thing or two about cannabis, you’ve probably heard of the endocannabinoid system (ECS). Researchers came across the components of this system while studying the effects of cannabis on the body. Eventually, they figured out that its components show up all over the body, from the brain and bones to the skin, digestive system, and immune system. They deemed the ECS the “universal regulator” of the human body, as it helps to keep everything in a state of balance, otherwise known as homeostasis.

The classical ECS features two receptors (CB1 and CB2), endocannabinoids that act as signalling molecules (anandamide and 2-AG), and enzymes that build and break down endocannabinoids. These components are also found throughout the immune system, where they help to control immune function, drive homeostasis, and modulate the immune system. A wide array of immune cells feature CB1 and CB2 receptors, including B cells, natural killer cells, monocytes, and CD8 and CD4 lymphocytes. Endocannabinoids bind to these sites and help to regulate processes such as the inflammatory response^[1].

How Cannabis Affects the Immune System

The intimate link between the ECS and the immune system opens up the possibility of cannabis working as a modulating agent of our physiological defences. You see, endocannabinoids (those found in the body) and phytocannabinoids (those found in plants) share a similar structure. This means that external cannabinoids, including THC and CBD, are potentially able to bind to ECS receptors, influence enzyme activity, and generally mimic endocannabinoids. As our endocannabinoids hold significant influence over our immune system, plant cannabinoids might serve as a way of “hacking” the ECS when it comes to immunity.

• Autoimmune Disorders

Sometimes the immune system goes haywire. In the case of autoimmune diseases, the cells that are supposed to protect us from outside invaders start to turn on our own bodily tissues; they mistake joints, skin, and nerve cells for aggressive bacteria and viruses. This self-inflicted damage leads to inflammatory cascades that result in symptoms such as fatigue, achy muscles, fever, hair loss, and rashes. Common autoimmune conditions include rheumatoid arthritis, psoriasis, and multiple sclerosis.

Early research has pitched cannabinoids against inflammation involved in autoimmune disease progression. Animal and cell studies also suggest that cannabis could exert an immunosuppressive effect.

• Cannabis and Multiple Sclerosis

Multiple sclerosis (MS) also autumns into the autoimmune category of diseases. The condition gives rise to symptoms of fatigue, pain, and muscle spasms as immune cells begin to attack the brain and nerves. The exact cause of MS remains unknown, but a combination of genetic and environmental factors is likely to blame. Researchers are eager to find out if cannabinoids can benefit the condition in any way, from neuroprotection to reducing immune activation. The medical advisors of the MS Society also believe that medical cannabis could help around 1 in 10 patients when it comes to muscle spasticity.

The spasticity associated with MS can also result in an overactive bladder, causing increased frequency and urgency of urination. Ongoing studies are looking to see if cannabinoids could help patients in this area. However, the results are mixed so far. Cannabinoid receptors certainly play an important role^[5] in the urinary bladder, but research published in The American Journal of Medicine suggests that cannabis use may increase the risk^[6] of an overactive bladder. Despite this data, other studies continue to assess the effects of cannabis extracts^[7] on incontinence in patients with MS.

• Risk of Viral Infection and Immunosuppression

If cannabis interacts with the immune system in a way that suppresses it, could it give viruses and other infectious pathogens an upper hand? It’s a possibility. Because of this effect, cannabis could predispose long-term and heavy users to an increased risk of acquiring and transmitting infections, and impaired immune function in general.

Even more worrisome, limited research also suggests that long-term cannabis use could trigger myeloid-derived suppressor cells (MDSCs), which suppress the immune system and may increase the odds of cancer. However, despite their effects on the immune system, ongoing studies are exploring some cannabis compounds for their impact on pathogenic viruses and bacteria.

• Cannabis and HIV

Human immunodeficiency virus (HIV) primarily spreads through unprotected sex. Once it enters the body, the pathogen acts as a parasite that lays waste to the immune system. In the early stages of infection, HIV causes flu-like symptoms and a significant reduction in CD4+ T cells that help to recruit other immune cells when faced with an infection. Following these initial symptoms, the virus continues to replicate but may not cause further symptoms for several years. Under the surface, however, it continues to impair and weaken the immune system, eventually causing a person to become immunocompromised.

Because researchers are exploring the immunosuppressive effects of cannabis, it seems logical that people living with HIV should avoid the plant. However, surveys show that many of them use the herb^[8]. As well as trying to figure out the dangers of cannabis in HIV patients, scientists are also seeing if cannabinoids can help to reduce viral replication and improve T cell counts^[9].

• Neurodegenerative Conditions

The autoimmune disease multiple sclerosis is characterised by neurodegeneration. Immune cells launch an inflammatory attack against the central nervous system. During this process, the cells develop a particular affinity for myelin—the protective and insulating coating that encases nerve cells. Over time, this assault damages the myelin and the nerve itself, which can cause problems with nervous system firing. Ongoing studies are looking at a potential neuroprotective effect^[10] of the CB1 receptor and compounds that bind to this site.

• Coronavirus

SARS-CoV-2, which causes the disease COVID-19, changed the world. Despite the worldwide vaccine rollout, cases continue to rage in many regions, and researchers are still on the hunt for therapeutics.

Some research teams have decided to probe cannabis for potentially useful molecules. Although certain cannabinoids may dial down the immune response, others are being explored for their direct effect on virus particles. Additionally, the deadlier end stages of COVID-19 are driven by inflammatory storms.

Currently, researchers from Portugal are testing blends of CBD and terpenes^[11] against SARS-CoV-2 infectivity. Other researchers are testing^[12] the cannabinoid acids cannabigerolic acid (CBGA) and cannabidiolic acid (CBDA) against SARS-CoV-2 entry into host cells.

Is Cannabis Good or Bad for the Immune System?

We don’t have enough data to provide a confident answer to that question. Some evidence suggests that the herb has immunosuppressive properties that could be beneficial; however, if this is true, it could also potentially cause problems in those with compromised immune systems, as well as healthy individuals that use the herb often. The bottom line: we need more human trials to ascertain a clear-cut answer.