Cannabis and Nausea: What You Need to Know

Nausea strikes for a variety of reasons, be it the result of an infection or morning sickness during pregnancy. Despite the numerous causes of nausea, it always manifests in the same way: an uneasy feeling in the stomach that often signals imminent vomiting. Interestingly, several cannabis-based medicines are approved for the treatment of nausea in very specific scenarios, and the endocannabinoid system presents itself as a promising therapeutic target. Does smoking weed help with nausea? You’re about to find out.

What Is Nausea?

Nausea. We’ve all felt this uneasy, queasy feeling at some point. Whether you drank too much the night before or went on a boat trip during choppy weather, you’ve probably felt nausea start to creep up on you in the past. But what exactly is nausea?

Nausea and vomiting are often thought of as synonymous; they’re different, but they share some similarities. Both are often signs of infection or other illnesses. Whereas vomiting involves the uncontrollable reflex that expels the contents of the stomach through the mouth, nausea involves a feeling of uneasiness in the stomach, often accompanied by the urge to vomit. However, feeling nauseated doesn’t always involve vomiting.

There are many different reasons why a person might feel nauseated. Some of the most common include:

Nausea serves a protective role in some instances, such as when we consume food contaminated with dangerous bacteria. However, sometimes it occurs when it doesn’t exactly seem necessary, such as when we feel anxious or are driving down a bumpy road. So, why does the sensation of nausea occur, exactly?

Why Nausea Occurs

Our bodies are a fascinating assembly of cells. They feature a range of automatic reactions aimed at keeping us safe. Accidentally place your hand on a hot surface, and your body will pull it away before you even have time to think about the pain. Walk into a dusty room, and your body will sneeze out those pesky particles without you making a conscious effort. Feeling nauseous, gagging, and eventually vomiting also falls into this category of protective procedures. However, people rarely have problems with excessive sneezing or muscle contractions (except in the cases of certain diseases). Nausea, on the other hand, often rears its head on random occasions, although it too accompanies a range of disease states.

The signal that triggers nausea stems from several distinct areas of the brain^[1]. For example, the area postrema detects certain vomiting-inducing substances in the blood, whereas the cerebellar and vestibular detect signals induced by motion that lead to feelings of nausea. These regions send signals to the nucleus tractus solitarius, which then induces a rise in vasopressin (a hormone that evokes nausea) levels and a response from the autonomic nervous system. Afferent signals from the GI tract, via the vagus nerve, also reach the nucleus tractus solitarius. These factors lead to gastric dysrhythmias and subsequent nausea.

Endocannabinoids in the Gut

We talk a lot about the endocannabinoid system (ECS) here at Royal Queen Seeds. Why? Because this body-wide network of signalling molecules, receptors, and enzymes partially underpins how cannabis affects the body. The ECS consists of two key receptors (CB1 and CB2), several signalling molecules, and anabolic and catabolic enzymes. But things don't end there; the expanded ECS, or endocannabinoidome (eCBome), consists of many more components and also provides regulatory functions.

Within this system, signalling molecules known as endocannabinoids are responsible for interacting with receptors to change the activities in cells and ultimately maintain homeostasis (biological balance). These chemicals are found almost everywhere in the body, including two anatomical areas largely involved in nausea: the gut and the brain. The two chief endocannabinoids that take part in this regulation are anandamide (also known as the “bliss molecule”) and 2-AG.

Within the gut, these molecules are tasked with fulfilling several key functions^[2], including:

The ECS also serves as an important regulator of the gut–brain axis^[3]—a bidirectional form of communication between the brain and peripheral nervous system components within the gut. This pathway links up regions of the brain responsible for emotion and cognition with peripheral gut functions. Hence, a wide array of factors—visual, auditory, and olfactory—can stimulate nausea.

Critically, cannabinoids from the cannabis plant (phytocannabinoids) are able to interface with the ECS in a similar way to endocannabinoids, as they share a similar molecular structure. Because endocannabinoids play a role in the regulation of nausea, action at the same receptor sites by way of phytocannabinoids, when applied in a clinical setting, could potentially offer similar results.

Does Weed Cause Nausea?

Before we delve into the research surrounding the possibility of cannabis helping nausea, we’re going to take a look at instances where substances in the plant can induce nausea. While some researchers are exploring the antiemetic properties of select cannabis constituents, others are finding out how some of them make us feel sick.

Many people who use cannabis frequently experience “greening out” at some point. Greening out refers to consuming too much cannabis, and experiencing nausea, vomiting, panic, and anxiety as a result; it encompasses uncomfortable sensations but doesn't equate to an overdose. When we inhale THC, the molecule binds to CB1 receptors in the central nervous system, which results in an acute rise of dopamine and the characteristic cannabis high. However, overstimulation of this site results in nausea and even vomiting in some users.

Cannabis Hyperemesis Syndrome

Cannabis hyperemesis syndrome (CHS), although rare, occurs in chronic cannabis users, and presents a more serious set of symptoms than simply greening out. After consuming high-THC cannabis, those with the condition experience cyclic nausea and vomiting, sometimes over the course of weeks, that could lead to hospitalisation.

The symptoms of CHS vary depending on the phase of the condition, but include early morning nausea, ongoing nausea, repeated episodes of vomiting, abdominal pain, dehydration, and reduced food intake and weight loss. Strangely, patients also frequently engage in compulsive bathing; many of them find that hot baths or showers help to relieve their symptoms.

But why does CHS occur? Several factors likely underpin the condition, including downregulation of CB1 receptors after prolonged cannabis use, mutations in the eCBome receptor site TRPV1, a deficiency in a liver enzyme (CYP2C9) that breaks down THC, and issues with dopamine signalling.

Does Weed Prevent Nausea?

Greening out and CHS aside, does cannabis help to relieve nausea? The studies remain early and inconclusive, but results so far appear promising.

It’s worth noting that the Food and Drug Administration (FDA) in the United States approved both dronabinol and nabilone (two synthetic versions of THC) for the treatment of chemotherapy-induced nausea and vomiting as a form of cannabinoid antiemetic therapy^[4]. The exact mechanism of action remains unknown, but both CB1 and 5-HT3 receptor activation likely play a major role.

Several other cannabis constituents^[5] also show early promise when it comes to nausea research, including THCA and CBDV.

Furthermore, while nausea has many causative factors, endocannabinoid tone (the amount of circulating endocannabinoids in the body) could play a role. For example, a study^[6] that exposed participants to parabolic flight manoeuvres to induce motion sickness found that the participants most affected had lower circulating levels of 2-AG. This endocannabinoid targets both the CB1 and CB2 receptors. Phytocannabinoids such as THC and caryophyllene also target this site.

Furthermore, CBD manages to inhibit the enzyme fatty acid amide hydrolase (FAAH), which breaks down anandamide and, to a lesser extent, 2-AG.

CBD and Nausea Prevention

Cannabidiol (CBD) has risen in prevalence over recent years as a non-psychotropic cannabinoid. But does the molecule offer any relief when it comes to nausea? Again, the research in this area remains early and limited.

Animal research^[7] conducted in 2011 found that CBD might help to buffer against nausea through action at serotonin receptors. A small human trial, conducted in 2016, administered Sativex (a combination of THC and CBD) to patients experiencing nausea due to chemotherapy. Despite interesting results, the medicine remains unapproved by the FDA. As well as binding to a range of eCBome receptors, CBD shows promise in raising endocannabinoid (molecules capable of combating nausea) levels by reducing the rate at which they’re broken down by catabolic enzymes of the ECS.

The Complex Relationship Between Cannabis and Nausea

Does smoking weed help nausea? What’s the best strain for nausea? No conclusive answers exist to these questions—yet. However, more research exists around nausea and medical marijuana than for many other conditions, which has paved the way for cannabis-based medicines as approved treatments for chemotherapy-induced nausea and vomiting.

Within the not-so-distant future, we should see more human trials emerge that put other cannabinoids to the test in this context. The science behind the ECS and eCBome in nausea regulation will also continue to develop, strengthening the argument to use and approve cannabis for different forms of nausea.