Does CBD Oil Work? The Science Behind Cannabidiol

What is CBD oil? What does science have to say about the extract's proposed health benefits?

Sabrina Stierwalt, PhD
4-minute read
Episode #305

Weed, pot, ganja, reefer, Mary Jane, cannabis. Whatever you call it, marijuana has been used for its supposed medicinal properties since ancient cultures experimented with the plant in China, the Netherlands, Egypt, India, and Greece. Its medicinal use is suspected to date back to more than 5,000 years ago in what is now present-day Romania.

Cannabidiol, or CBD, one of marijuana’s active ingredients which has seen a recent surge in popularity, was discovered almost 80 years ago. Depending on whom you ask, CBD oil can relieve pain, aid sleep, inspire appetite, ease stress and anxiety, act as an anti-inflammatory or an analgesic, boost the immune system, assist memory, and ease asthma-related symptoms. But despite these widespread applications, the medical effects of CBD are still debated.

If we’ve known about the potential health benefits of CBD specifically and marijuana more generally for so long, then why hasn’t science come down more conclusively either to support or refute these claims? The reason is in large part because, at least in the US, the federal government classified marijuana as a “Schedule I” drug, alongside heroin, LSD, and ecstasy, back in the 1970s. Schedule I drugs have “no currently acceptable medical use and a high potential for abuse” and thus are very difficult to study in the laboratory due to the administrative hurdles.

Difficult...but not impossible. So let’s take a look at what we do know from scientific studies about the health benefits of CBD oil.

What is CBD oil?

Tetrahydrocannabinol (THC) is the main psychoactive or mind-altering ingredient in marijuana. Cannabidiol, or CBD, is another prevalent component of marijuana (and hemp) plants that is considered by many to have medicinal benefits but without the same “high” associated with THC. CBD is typically extracted from the plant and sold as a concentrated liquid. Just as with other herbal extracts, that extraction process can vary and thus so can the additional chemicals found in the resulting cannabis oil.

Although the US Drug Enforcement Administration is wary enough of marijuana to classify it as a Schedule I drug, CBD on its own does not cause a “high” and two years ago the US Food and Drug Administration eased regulations on CBD that make it easier to research. The World Health Organization also notes that CBD “exhibits no effects indicative of any abuse or dependence potential.”

What are the proposed health benefits of CBD oil?

CBD oil and epilepsy

Among the “strongest scientific evidence” for the effectiveness of CBD, according to Harvard Health, is that CBD can reduce the number of seizures experienced by children with different epilepsy syndromes. In fact, the only FDA-approved use of CBD is in the drug Epidiolex, which treats two rare but very severe forms of childhood epilepsy.

The phrases that comes up most commonly in the scientific literature surrounding CBD use for non-epilepsy related health issues are “considerable potential” and “need for further study.” For example, studies suggest that the anti-inflammatory and anti-oxidant nature of CBD make the extract a strong candidate for helping patients with diabetes and heart disease. CBD can reduce pressure in the eye (called intraocular pressure) and thus may work as a treatment for glaucoma. However, these studies are still “pre-clinical,” meaning that these benefits are so far only a hypothesis, and there are many stages of trials that still have to be conducted to draw a clear connection.

CBD oil and anxiety

Other, mostly pre-clinical or mice-based studies, suggest that CBD might help people suffering from anxiety, panic attacks, obsessive-compulsive disorder, and post-traumatic stress.

In 2012 in a German study actually involving humans, CBD was found to reduce psychotic symptoms like hallucinations and scattered thinking in patients with schizophrenia.

CBD oil and cancer

One study also found that CBD reduced the proliferation, invasion, and metastasis of human breast cancer cells grown in dishes, highlighting a possible non-toxic route toward thwarting cancer progression. However, the American Cancer Society warns that, although cannabinoids have so far been found to be safe in treating cancer, they should not be used as the only method of treatment as studies have not conclusively shown that they help control or cure it.

Research into other purported CBD benefits have been less conclusive. For example, CBD was found “safe but not effective” in treating Crohn’s Disease in a study of 20 patients.

CBD oil side effects

There are reasons to be wary of extensive CBD use as well. CBD does come with side effects, including nausea, fatigue, and changes in appetite. (Although these side effects are less problematic than those associated with other anti-seizure medications.) It may also lead to increased levels of certain types of blood thinner in your blood. Perhaps most importantly, CBD is considered a supplement, at least in the US, which means its safety and purity are not regulated by the FDA. So there is no way to know if the contents of your CBD oil are as promised on the label.

Our limited understanding of CBD’s health benefits also means that we don’t yet know what the proper dosage is for addressing different ailments. The fraction of a cannabis oil dose that a person absorbs and how long it stays in their system also vary widely depending on the person, making dosages even harder.

Is CBD oil legal?

In 2016, Forbes reported predictions that CBD could become a $2-3 billion industry by 2020. This will no doubt be due in part to the increase in legal access to the extract and to marijuana itself. In September of 2018, the FDA placed certain drugs containing CBD, like Epidiolex, into Schedule V, or the least restricted category of drugs. Biologists are also working to grow strains of marijuana that have lowered THC content and increased production of CBD. More broadly, cannabis is legal for medical use in 23 states in the United States as well as in Israel, Canada, and the Netherlands. Uruguay has also voted to legalize it.

So while we may start to see more CBD oil being offered in smoothies or as add-ons at coffee shops, we also may see more concrete research on whether or not we can credit CBD with as many health benefits as its supporters would like.

Please note that archive episodes of this podcast may include references to Ask Science. Rights of Albert Einstein are used with permission of The Hebrew University of Jerusalem. Represented exclusively by Greenlight.

About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.