How Cannabis Can Help Nausea

There is now a consensus among the medical community that cannabis is a helpful treatment for nausea and vomiting. Clinical studies, primarily on patients with cancer, show that cannabinoids like THC and CBD can reduce these challenging symptoms — often better than conventional anti-emetics and with less worrisome adverse effects. In addition, the endocannabinoid system regulates nausea, which explains why cannabinoids are able to impact nausea so strongly. Still, patients should be cautious of cannabinoid hyperemesis syndrome — a rare reaction to heavy cannabis use that actually causes cyclic vomiting and can be fatal to those affected.

Research on nausea and cannabis

The cannabis plant has a long history of being used for nausea and vomiting. In fact, cannabis is one of the oldest known human remedies for nausea and has been used for this purpose for thousands of years. Treatment of nausea was also one of the first medical benefits of cannabis recognized by the modern medical community, and is one of the most well-supported uses for cannabis, based on research.

The main body of research looking at cannabis for nausea comes from studies on cancer sufferers, who often experience severe nausea and vomiting with therapy. There is also positive data on using cannabis for nausea in patients with HIV. Both conditions (and their treatments) can cause severe nausea. Interestingly, treating this nausea was one of the medical uses of cannabis that helped motivate the medical cannabis legalization effort. In fact, treating nausea from cancer and HIV was one of the medical uses for cannabis that spurred on the legalization movement in early years. Doctors in the 1970’s and 1980’s knew that the available options helped patients vomit less, but many still had severe nausea that was resistant to treatment. Symptoms of nausea can be so intense, up to 20% of cancer patients were discontinuing potentially life-saving chemotherapy treatment because of this side effect. When it became clear that cannabis was helping many patients with this debilitating side effect, it pushed researchers to study it in depth and advocate to fight for cancer and HIV patients’ right to use cannabis as a nausea reliever.

Now reviews of the literature confirm that there is substantive evidence that cannabis can aid in nausea relief.

For one thing, the research on cannabis for nausea includes multiple human clinical trials, which show cannabis can be as effective as other modern treatments for nausea — and even more effective than some.

For example, clinical trials on nabilone and dronabinol, synthetic versions of THC (the most common cannabinoid in the cannabis plant) have shown improvement in nausea relief for cancer patients and reduce vomiting episodes significantly. In some cases adding these cannabinoids to the conventional treatment, like dopamine receptor antagonists, improved results, and in other cases switching to cannabinoids alone was more effective than the conventional control.

Other studies show that THC from cannabis can also significantly suppress nausea and vomiting when compared to both placebos and conventional treatments — sometimes matching the efficacy of conventional treatments, and sometimes surpassing them.

Researchers have also looked at Δ8-THC (a cannabinoid similar to THC but with less psychoactive effects) as a nausea reducer in children. This research found that Δ8-THC can also aid in nausea relief by reducing anticipatory nausea, the nausea that occurs from thinking about or encountering something that’s made you sick in the past.

CBD and nausea

CBD (another cannabinoid that lacks THC’s disorienting psychoactive effects) may also be helpful in the treatment of nausea. While human trials have yet to look at CBD alone, a recent animal study suggests that CBD may also relieve nausea and vomiting, as mice treated with CBD showed reduced nausea related behaviors.

In addition, adding CBD to a THC treatment may also be helpful. Often standard anti-nausea drugs only delay nausea rather than eliminating it. One study found that Sativex (a cannabinoid medicine containing an even blend of THC and CBD) taken in conjunction with other anti-emetic therapies, could reduce or eliminate delayed nausea in patients.

Still, it’s notable that some research suggests CBD only helps with nausea in lower doses, and can cause nausea if the dose is too high. Again, we often see this biphasic effect with cannabis and dosing is critical for establishing benefit and avoiding side effects.

How cannabis works on nausea

The endocannabinoid system (ECS) exists in all vertebrates and helps regulate crucial functions such as sleep, pain, and appetite. The human body produces its own cannabinoids, which modulate and activate its various functions, but as its name suggests, the endocannabinoid system can also be modulated and activated by cannabinoids found in the cannabis plant. Because the entire system was only discovered in the past 30 years, scientists still have much to learn about the myriad ways cannabis affects the human body.

Interestingly, nausea is another crucial function that is largely regulated by the ECS, and modulation of this system is the primary way that cannabis can impact our nausea response.

While we have little data from human studies on this, a large body of animal studies have highlighted how this works. One human study that is relevant though, shows that naturally produced cannabinoids in the human body (called endocannabinoids), anandamide and 2-AG, tend to be lower in humans who experience motion sickness. These patients also had less CB1 receptors, a primary receptor in the endocannabinoid system; and inducing motion sickness with parabolic flight maneuvers led to an increase in anandamide early on and an increase of 2-AG later on, suggesting that this system is actively involved in reducing nausea responses.

In animal studies, the connection between the ECS and nausea is even more established. Studies on a wide variety of animals shows that cannabinoids can reduce nausea by stimulating the CB1 receptor. Stimulating CB1 (such as with substances like THC) normally suppresses nausea and vomiting, while substances that cause an opposing activation promote nausea and vomiting.

In addition, CBD seems to work through a different route. It doesn’t interact easily with CB1, but recent studies show that it can stimulate serotonin receptors, which can lead to reduced nausea.

Using cannabis for nausea

When it comes to the practical side of using cannabis for nausea, there hasn’t been much research comparing different ways of using cannabis. Still, research shows positive results for cannabis on nausea whether it is used in edible, sublingual or inhaled formulations. It’s worth noting that many patients say they prefer inhaled methods for nausea, often because it’s easier for patients to find the right dose, it is easier to inhale than eat something when you are feeling nauseous, and it starts working more quickly than edibles. Absorption is also more efficient by inhaling when there are GI issues in general.

One small study compared oral to smoked cannabis and found many patients were able to achieve better results using inhaled cannabis.

When it comes to the cannabinoids to use, most research looks at THC-based cannabis medicines for nausea, so that is the option best supported by the research, but there are also studies showing CBD, a blend of CBD and THC or Δ8-THC could be helpful as well.

Potential side effects of cannabis use

One important side effect to mention is that chronic heavy cannabis use can lead to a condition called cannabinoid hyperemesis syndrome, a condition characterized by intractable cyclic vomiting. While rare, it can be fatal if cannabis use is continued, so those using cannabis for nausea should be particularly careful of this side effect. One trait of the condition is that relief can be found from hot baths and showers. If this symptom is experienced, it is a sign that cannabis may be causing additional nausea and vomiting.

In addition, the studies on humans using cannabis for nausea found that common side effects were feeling high, euphoria, dizziness, sedation, depression, paranoia, arterial hypertension and confusion.