cbd side effects

Potential Side Effects of CBD

What are the Potential Side Effects of CBD?

Along with THC, CBD (cannabidiol) is the second most common chemical compound found in marijuana. Unlike its psychoactive counterpart which is largely responsible for the uplifting effects of marijuana, CBD can work in the opposite way, blocking the effects of THC.

Both THC and CBD interact with the human endocannabinoid system, a group of cell receptors and molecules specifically designed to interact with chemical compounds found in the cannabis plant (cannabinoids). THC shows a greater affinity for the CB1 receptors, while CBD interacts with type-2 cannabinoid receptors, as well as neurotransmitters which regulate the release of various brain chemicals.

Unlike THC, which is more connected with the recreational use of marijuana, CBD has a wide range of medicinal effects on the body. There has been an increasing number of studies that indicate that CBD has anti-tumoral, antioxidant, anxiolytic, anti-convulsing and neuroprotective properties. Science is still unclear as to how CBD works, but anecdotal evidence and pre-clinical research are showing promise.

Is CBD Perfectly Safe?

cbd side effectsMany people all over the world use CBD oils, extracts and concentrates for their conditions. Medical CBD users swear by its efficacy, although lack of extensive research creates a shroud of mystery regarding this new alternative drug. What could the side-effects be?

Studies from as early as 1986 (Consroe et al.) report that CBD had negative effects in people with Parkinson’s disease. According to the researchers, the side effects experienced by the CBD oil were mild and included hypotension (low blood pressure) as well as dry mouth, lightheadedness and sedation

A research performed in 2011[1] reviewed and analyzed reports from various cases in which CBD was administered to patients. The paper concluded that CBD is safe for consumption and is non-toxic even in higher doses of up to 1,500mg/day and that

controlled cannabidiol administration is safe and non-toxic in humans and animals. It also does not induce changes in food intake; nor does it affect physiological parameters like heart rate, body temperature or blood pressure.

However, the study did find out some instances in which CBD had adverse effects to some patients, including the “inhibition of hepatic (liver) drug metabolism, alterations of in vitro cell viability, decreased fertilization capacity, and decreased activities of p-glycoprotein and other drug transporters.”

The 2011 research by Bergamaschi et al was extended in 2017[2] by another group of researchers who reviewed the safety and side effects of CBD. They used the many studies on CBD which were conducted between 2011 and 2017. These provided an additional 74 articles to examine. The extended research confirmed the findings of the first, adding fatigue, diarrhea and appetite changes in the list of CBD side effects.

The Side Effects of CBD Oil

When put in medical terms, the side effects of CBD seem much more serious than they really are. Let’s see them one by one to determine their severity.

Inhibition of Hepatic Drug Metabolism

A potential side effect of CBD has to do with the liver’s ability to process certain drugs and medications. According to the study, CBD inhibits the activity of some liver enzymes (called cytochrome P450) and prevents the liver from metabolizing certain pharmaceutical drugs. This is essentially the same effect that CBD has with THC as well, as it negates its effects. What’s interesting with this side-effect is that it’s so mild, it can be compared with eating a grapefruit to reduce the effects of medication. So, despite its scary name, inhibition of hepatic drug metabolism, is really not a major side effect.

Fatigue, Diarrhea and Appetite Changes

The study by Iffland et al in 2017 found that “fatigue” was the most common adverse effect felt by patients treated with high-CBD strains. Moreover, they observed that appetite increased less among this group of patients.

The most reported side effects in the study were: 21% tiredness, 17% diarrhea, and 16% reduced appetite. In a few cases, severe side effects occurred, but it is not clear if these were caused by CBD or other factors.

CBD and Parkinson’s Disease

Although studies by Consroe et al. in 1986 concluded that CBD oil can worsen symptoms of tremor in patients with Parkinson’s disease, newer research debunks this claim. In a study published in 2008[3], researchers claim that “CBD did not worsen the motor function and decreased the total scores of the Unified Parkinson’s Disease Rating Scale”. They also added that no side effects were observed during the treatment, suggesting that CBD might as well be used for the treatment of other symptoms of Parkinson’s, such as psychosis.

Using CBD Oil The Right Way

Like all drugs, in order to minimize the chances of experiencing side effects from CBD, it is important to use the correct dose and always obtain CBD oil, CBD concentrate or CBD extracts from credible sources. As the market is still nascent, there are many vendors selling inferior CBD products, that can even be dangerous for your health.

To enjoy the benefits of CBD, use the smallest dose and work your way up. Because side effects naturally increase with dosage, a smaller dose means you will have a lesser chance of experiencing negative side effects. However, you can rest assured that even the worst side effects of CBD won’t be worse than eating a slice of grapefruit!


[1] Bergamaschi MM, Queiroz RH, Zuardi AW, Crippa JA. Safety and side effects of cannabidiol, a Cannabis sativa constituent. Curr Drug Saf. 2011 Sep 1;6(4):237-49. Review. PubMed PMID: 22129319.

[2] Iffland K, Grotenhermen F. An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies. Cannabis and Cannabinoid Research. 2017;2(1):139-154. doi:10.1089/can.2016.0034.

[3] Zuardi AW, Crippa JA, Hallak JE, Pinto JP, Chagas MH, Rodrigues GG, Dursun SM, Tumas V. Cannabidiol for the treatment of psychosis in Parkinson’s disease. Psychopharmacol. 2009 Nov;23(8):979-83. doi: 10.1177/0269881108096519.