Cannabis is celebrated for the benefits it offers in the management of certain medical conditions. As awareness around cannabis grows, consumers are becoming better versed in the therapeutic potential of cannabinoids in the treatment of specific autoimmune diseases, inflammation, and gastrointestinal disorders. 

But how does cannabis affect the immune system as a whole? If you’re a regular consumer, you may have pondered whether cannabis weakens or boosts your immune system. Can frequent cannabis use render you more prone to infections or contagious diseases?

As it turns out, research into cannabis and the immune system hasn’t historically piqued the interest of scientists. However, as our understanding of the effects of cannabis on the body becomes more sophisticated, we need to also broaden our knowledge of how cannabis influences the immune system. 

Present evidence suggests that cannabis can suppress immune system function. While this can be helpful for individuals with autoimmune illnesses, it may not be so beneficial for those with functional immune systems.

The immune system is one of the body’s most sophisticated networks. A collection of specialized cells, endogenous chemicals, and organs work in concert to ward off pathogens and infections, protecting the health and homeostasis of the body. 

The immune system is multifaceted, and its core components that actively combat infection include white blood cells, the complement system, antibodies, the lymphatic system, the spleen, the thymus, and bone marrow, but we’ll mainly talk about white blood cells. 

Memories of every microbe previously defeated by the immune system are logged in white blood cells. These memories enable the fast tracking and elimination of infections that have already been experienced. The immune system is also responsible for detecting and eradicating malfunctioning cells.

The knowledge we have about the interaction of cannabis with specific immune elements is limited. While there is some research exploring the effects of cannabinoids on white blood cell count and the lymphatic system, we know less about how cannabis impacts the thymus or the complement system.

An elegant connection exists between the body’s endocannabinoid system (ECS) and its immune system. The ECS is generally considered to be one of the gate-keepers of the immune system, preventing the onset of overwhelming inflammatory responses that may result in disease. The ECS can also influence the function of immune cells. 

CB1 and CB2 receptors in the endocannabinoid system mediate the effects of cannabis within the immune system. The two major cannabinoids, THC and CBD, appear to have distinctive effects on the immune system due to their unique interactions with cannabinoid receptors. Abundant literature suggests that cannabinoids affect the functions of most types of immune cells. 

A 2020 review found robust evidence that CBD suppresses certain inflammatory responses in the immune system and may induce cellular death in immune cells. Immune cell death isn’t always a bad thing—it’s a normal part of the cellular life cycle, and helps to protect a person by alleviating inflammatory responses. 

Like CBD, THC also suppresses immune activity, dialing down inflammatory responses. THC has also been shown to alter the function of immune cells responsible for antimicrobial activity.

When scientists discuss cannabis and the immune system, they often discuss its effects as immunomodulatory or immunosuppressive. Immunomodulation refers to any therapy that modifies the immune system response. When cannabis suppresses the expression of aspects of the immune system, this form of modulation is known as immunosuppression. 

It’s vital to point out here that marijuana’s ability to subdue or suppress immune system cells can be useful if the immune system is dysregulated and in need of suppression. If not, immune suppression might not be helpful. 

Research published in 2017 indicated that both CBD and THC have an immunomodulatory effect on the human intestinal lymphatic system, the major host of immune cells. The lymphatic system also contains more than half the body’s lymphocytes—white blood cells that play a critical role in finding and destroying foreign cells or substances that have infiltrated the body.

The study’s authors found that oral administration of CBD and THC with fats resulted in extremely high cannabinoid levels in the intestinal lymphatic system: CBD concentrations in lymph cells were 250 times higher than in plasma, while THC concentrations in lymph cells were 100 times higher than in plasma. 

So, what’s the significance of this? For individuals with autoimmune diseases, cannabis can achieve higher concentrations in the lymphatic system and suppress unhealthy inflammatory immune responses more successfully.

Research carried out in 2003 on healthy volunteers suggests that regular cannabis may subdue immune function. Cannabis users were found to have fewer proinflammatory cells and more anti-inflammatory cells. 

While less potential for inflammation may sound like a win, in this case, it was associated with a significant reduction in white cell functionality, and impaired white cells can mean a hindered ability to fight off infections. Regular cannabis users also had decreased amounts of natural killer cells, which limit the spread of tumors and microbial infections. 

The study also indicated that there may be a dose-response relationship between cannabis use over an individual’s lifetime, and a decrease in certain immune system markers, meaning those who use cannabis regularly may be more susceptible to the progression of infectious disease. 

What about the effects of cannabis on extremely immunocompromised individuals? Unfortunately, cannabis can substantially decrease infection-fighting cells in people undergoing chemotherapy. This suppressive response may further add to the detrimental effects of chemotherapy on immune systems of those with cancer. 

Research on people with HIV+ and AIDS, who are particularly vulnerable to infections, however, indicates that there is no firm evidence that cannabis adversely affects immune function. 

Instead, findings suggest cannabis use among HIV+ patients may enhance the immune system by producing a statistically significant decrease in viral load and an increase in CD4 cells. CD4 cells can be considered a marker that indicate the robustness of the immune system.

While existing research allows us to glean insights into cannabis and the immune system, we need more rigorous data to paint broad brushstrokes. According to the most recent 2017 report from the National Academies of Science, Engineering, and Medicine (NASEM), there’s insufficient research on the effects of cannabis or cannabinoid-based medicines on the human immune system to draw firm conclusions. 

Within the current global climate shaped by COVID-19, there’s an impulse among the research community to enhance our understanding of the impact of cannabis on the immune system. Some cannabis researchers are currently channeling their focus into investigating whether cannabis may be helpful or harmful in treating COVID-19. 

More profound exploration into the effects of cannabinoids on the immune system is also being encouraged. Watch this space as new frontiers are forged.

Emma Stone

Emma Stone is a journalist based in New Zealand specializing in cannabis, health, and well-being. She has a Ph.D. in sociology and has worked as a researcher and lecturer, but loves being a writer most of all. She would happily spend her days writing, reading, wandering outdoors, eating and swimming.