“If the CBD is from a reputable source and one that has been inspected by a third-party independent lab, the content of CBD is more reliable,” notes Dr. Matharu-Daley. “The CBD should be organically grown, free of pesticides and heavy metals, and not sourced in food which can affect absorption. Generally, CBD is safe and side effects are few at low doses.”
Because CBD supplements come in so many different forms—such as oils, gummies, tinctures, and vapors—the amount that’s actually absorbed can vary drastically. This, combined with each person, will ultimately affect which (if any) CBD side effects you might experience.
There are several reasons why someone might want to use CBD. The substance can be found in a multitude of products ranging from pain-relieving creams to edible tinctures to skincare. Research is still underway, but over the last few decades scientists have become more aware of how CBD might prove beneficial when applied either topically or ingested.
CBD Is Still an Unregulated Substance
In some cases, those who ingest CBD supplements might experience nausea, says Dr. Matharu-Daley. This depends on how sensitive the person is to CBD, as well as the amount they ingest.
It’s important to point out that CBD is not regulated by the FDA and therefore dosages might not be accurate. It’s also difficult to know what an appropriate dose is the first time you try a new product.
Steven Gans, MD is board-certified in psychiatry and is an active supervisor, teacher, and mentor at Massachusetts General Hospital.
The most comment side effects of CBD include drowsiness, gastrointestinal issues, dry mouth, reduced appetite, nausea, and interaction with other medications. Those are outlined in detail below.
Human studies evaluating the use of CBD in treating chronic pain are lacking. Those that do exist almost invariably include THC, making it difficult to isolate CBD’s distinct effects.
Among the few human trials evaluating CBD’s anxiolytic effects was one published in the Brazilian Journal of Psychiatry in 2019. For this study, 57 men were given either CBD oil or a placebo before a public-speaking event. Anxiety was evaluated using physiological measures (such as blood pressure, heart rate, etc.) and a relatively reliable test for mood states known as the Visual Analog Mood Scale (VAMS).
Outside of these two disorders, CBD’s effectiveness in treating seizures is uncertain. Even with Epidiolex, it is uncertain whether the anti-seizure effects can be attributed to CBD or some other factor.
In addition, the stroke volume (the amount of blood remaining in the heart after a heartbeat) was significantly reduced, meaning that the heart was pumping more efficiently.
CBD’s exact mechanism of action is unclear. Unlike THC, CBD has a relatively low affinity for cannabinoid receptors in the brain. These are the molecules to which THC binds to elicit its psychoactive effects.
But, ultimately, if you like it, you’re not experiencing bothersome or dangerous side effects, and feel like it works, that’s what matters most.
The lack of regulation has also left the door open for products to be subject to both “contamination and adulteration,” Dr. Tishler says. One study, published in JAMA in 2017, found that almost 70 percent of CBD products—including vape cartridges, tinctures, and oils—sold online did not contain the things they claimed to in the right amounts. That’s why Boehnke recommends only buying CBD products that you can verify (via a certificate of analysis) do contain what they’re supposed to. And Boenhke offers the same advice he does for all cannabinoid products: Start at a low dose and, if you decide to increase it, go slowly. (Start low, go slow.)
Nevertheless, how do we account for all the people out there (like me) who use these products and feel like they’re doing something? Beyond the placebo effect, it’s possible that something else in the cream could be doing the heavy lifting here. These products don’t just contain CBD, Dr. Tishler points out. In fact, many of them also come with ingredients like arnica, menthol, or camphor, which may all provide a more immediate sensation of soothing or pain relief. So it could be those ingredients (or just the act of massaging the balm into your skin) that makes you feel better.
So…is CBD cream just an expensive placebo?
But some studies have found essentially zero side effects of high-dose CBD (900mg) and those that researchers do see—like drug interactions—aren’t considered to be issues when CBD is used topically.
When the National Academies of Sciences, Medicine, and Engineering evaluated decades of cannabis research, they concluded that "in adults with chronic pain, patients who were treated with cannabis or cannabinoids are more likely to experience a clinically significant reduction in pain symptoms."
If you’re ingesting something that only has CBD in it and no THC, you won’t have significant effects in the brain. This is why CBD is often referred to as being “non-psychoactive,” although that’s clearly a bit of an oversimplification because it does do something to the central nervous system.
In fact, the most compelling research they found for using cannabinoids for pain came from a large review and meta-analysis published in JAMA in 2015. For the study, researchers looked at results from 79 previous studies of cannabinoids and various medical conditions, including chronic pain. However, of those studies, only four involved CBD (without THC)—none of which were looking at pain. So although we might assume that CBD is doing something to help address pain—according to the studies involving the whole cannabis plant—we don’t have great evidence to prove it.