CBD. Cannabidiol. No matter what you call it, you may have heard health claims about this little-known part of the marijuana plant, which comes from the plant's flowers. Some say it treats muscle aches, anxiety, sleeping troubles, chronic pain, and more.

But what does the science say?

We spoke to NIH expert Susan Weiss, Ph.D., to learn more and find out why consumers should be careful. Dr. Weiss is the director of the division of extramural research at the National Institute on Drug Abuse (NIDA).

What is CBD?

CBD (or cannabidiol) comes from the cannabis (or marijuana) plant.

The chemical compound THC [tetrahydrocannabinol] is the part of the cannabis plant that most people are familiar with because that is the part that makes people “high.” Most effects of marijuana that people think of are caused by THC.

Most recreational marijuana has very little CBD in it. CBD products are available through dispensaries, health food and convenience stores, and the internet. It's a widely used product that's not regulated—and is not legal to sell for its largely unproven health benefits.

How does CBD work?

Nobody really knows what is responsible for the mental and physical health benefits that have been attributed to it. CBD affects the body's serotonin system, which controls our moods. It also affects several other signaling pathways, but we really don't understand its mechanisms of action yet.

How much do we know about CBD as a potential treatment?

There are over 50 conditions that CBD is claimed to treat.

We do know that CBD can help control serious seizure disorders in some children (e.g., Dravet and Lennox-Gastaut syndromes) that don't respond well to other treatments. Epidiolex is an FDA [Food and Drug Administration] approved medication containing CBD that can be used for this purpose.

There's also data to suggest the potential of CBD as a treatment for schizophrenia and for substance use disorders. But these potential uses are in extremely early stages of development.

Are there side effects?

We don't know of any severe side effects at this time. But there were mild side effects reported in the epilepsy studies, mostly gastrointestinal issues like diarrhea. There were also some reported drug-to-drug interactions. That's why, for safety reasons, it's important that CBD or any cannabis product go through the FDA review process.

Are there any specific CBD studies that you are focused on?

We are interested in CBD as a potential treatment of substance use disorders.

There is some research looking at it for opioid, tobacco, and alcohol use disorders. If CBD can help prevent relapse in those areas, that would be really interesting. We're also interested in it for pain management. Trying to find less addictive medications for pain would help a lot of people.

What else would you like people to know?

Buyer beware.

We are concerned about the health claims being exaggerated or incorrect. The FDA issued warning letters to several companies because of untested health claims. And the CBD products themselves didn't always contain the amount of CBD that they were reported to have—some actually had THC in them.

Another concern is that people are using CBD to treat ailments for which we have FDA-approved medications. Thus, they may be missing out on better treatments. And when they're using CBD or other cannabis products for conditions we don't know very much about, that's worrisome. 

FDA has not approved any CBD products except for one prescription drug to treat rare, severe forms of seizure disorders in children. It is still unclear whether CBD has any other benefits.

Other than the one approved prescription drug, CBD products have not been evaluated or approved by FDA for use as drug products. This means that we do not know:

• if they are safe and effective to treat a particular disease
• what, if any, dosage may be considered safe
• how they could interact with other drugs or foods
• whether they have dangerous side effects or other safety concerns

The clinical studies that supported the approval of the one available CBD drug product identified risks related to the use of CBD, including liver toxicity (damage), extreme sleepiness, and harmful interactions with other drugs.

1. CBD has the potential to harm you, and harm can happen even before you become aware of it.

   • CBD can cause liver injury.
   • CBD can affect how other drugs you are taking work, potentially causing serious side effects.
   • Use of CBD with alcohol or other drugs that slow brain activity, such as those used to treat anxiety, panic, stress, or sleep disorders, increases the risk of sedation and drowsiness, which can lead to injuries.
   • Male reproductive toxicity, or damage to fertility in males or male offspring of females who have been exposed, has been reported in studies of animals exposed to CBD.

2. CBD can cause side effects that you might notice. These side effects should improve when CBD is stopped or when the amount used is reduced.

   • Changes in alertness, most commonly experienced as somnolence (drowsiness or sleepiness).
   • Gastrointestinal distress, most commonly experienced as diarrhea and/or decreased appetite.
   • Changes in mood, most commonly experienced as irritability and agitation.

3. There are many important aspects about CBD that we just don’t know, such as:

   • What happens if you take CBD daily for sustained periods of time?
   • What level of intake triggers the known risks associated with CBD?
   • How do different methods of consumption affect intake (e.g., oral consumption, topical , smoking or vaping)?
   • What is the effect of CBD on the developing brain (such as on children who take CBD)?
   • What are the effects of CBD on the developing fetus or breastfed newborn?
   • How does CBD interact with herbs and other plant materials?
   • Does CBD cause male reproductive toxicity in humans, as has been reported in studies of animals?

There is no comprehensive research studying the effects of CBD on the developing fetus, pregnant mother, or breastfed baby. FDA is continuing to collect and study the data on the possible harmful effects of CBD during pregnancy and while breastfeeding. However, based on what we do know, there is significant cause for concern.

High doses of CBD in pregnant test animals have caused problems with the reproductive system of developing male fetuses. In addition, based on what we already know about CBD, we expect that some amount of CBD will be transferred to babies through breast milk.

We also know that there is a potential for CBD products to be contaminated with substances that may pose a risk to the fetus or breastfed baby, including THC. We have also heard reports of CBD potentially containing other contaminants (e.g., pesticides, heavy metals, bacteria, and fungus); we are investigating this.

Moreover, CBD has known risks for people in general. Based on clinical studies in humans, risks can include the following:

• liver toxicity (damage)
• extreme sleepiness
• harmful interactions with other drugs

FDA is studying the effects of CBD use from different angles, such as: (1) the use of CBD-containing products, like food, cosmetics, or supplements, over a person’s entire life; and (2) the effects of using these various products in combination. There are many unanswered questions about the science, safety, and quality of products containing CBD.

We especially want to learn more about the effects of CBD during pregnancy and while breastfeeding, including, for example, whether and to what extent the presence of CBD in human milk harms the breastfed baby or the mother’s milk production.

Cannabidiol (CBD) is a compound found in marijuana. CBD is not impairing, meaning it does not cause a “high.”

CBD can be derived from hemp or from non-hemp plants. Hemp is defined as any part of the cannabis sativa plant with no more than 0.3% of tetrahydrocannabinol (THC), the mind-altering substance in marijuana.

CBD Use in the United States

In 2018, the U.S. Congress passed and signed into law the Agriculture Improvement Act. This law removed hemp from the federal Controlled Substances Act, effectively legalizing CBD if it comes from hemp. However, a few states have not removed hemp from their state’s controlled substances acts, so legality of CBD products differs across states.

CBD is marketed in many consumer products:

• Foods
• Oils
• Lotions
• Capsules
• Cosmetics

How Can CBD Affect Your Health?

Is CBD a medicine?

Scientists are still learning about how CBD affects the body. The U.S. Food and Drug Administration (FDA)  approved Epidiolex, a medicine that contains purified CBD from hemp, to help treat rare seizure disorders. The FDA has concluded that this drug is safe and effective for this intended use. However, other marketed products and uses of CBD may not be FDA approved.

Potential harms and side effects

Using CBD products is not risk free. The FDA has limited data on CBD safety. Please consider these possible side effects and risks before using CBD:

• Liver damage
• Interference with other drugs you are taking, which may lead to injury or serious side effects
• Drowsiness or sleepiness
• Diarrhea or changes in appetite
• Changes in mood, such as irritability

Using CBD during pregnancy is not recommended.

CBD use during pregnancy is not recommended. The potential health effects of using CBD products during pregnancy are currently unknown. In animals, high doses of CBD have caused negative effects on developing fetuses.

We do not know if CBD is passed to a baby through breast milk. Since negative effects have been associated with CBD use, people who are breastfeeding are encouraged to avoid CBD.

Keep CBD products away from children

We do not know the effects of CBD on children’s developing brains. If you use products that contain CBD or THC, keep them in childproof containers and out of the reach of children.

For additional questions, contact your healthcare provider, your health department, or your local or regional poison control center at 1-800-222-1222, or 911 if it’s an emergency.

Unknowns

There is a lot we do not know about CBD. Currently, we do not know how CBD use affects a person over time. We also do not know how different modes of CBD use (smoking, vaping, eating, applying to skin, etc.) affect a person.

Risk of Unintentional Poisoning

Many businesses that sell hemp and CBD products also sell products that contain THC. Individuals should be careful to not mistake THC products for hemp or CBD products. Products containing THC can result in psychoactive effects and adverse events. Additionally, most CBD products are not regulated by the FDA. As such, consumers should be aware that products labeled as hemp or CBD may contain other ingredients, such as THC, pesticides, heavy metals, bacteria, or fungi.

CDC released a Health Alert Network (HAN) Health Advisory in 2021 to inform consumers that CBD can be synthetically converted into Delta-8 THC, which is psychoactive and not well understood. This alert warns consumers about the potential for adverse events due to insufficient labeling of products containing THC and CBD.

If consumers experience adverse effects of THC- or CBD-containing products that are an immediate danger to their health, they should call their local or regional poison control center at 1-800-222-1222 or 911 or seek medical attention at their local emergency room and report the ingredients of products they have consumed to healthcare providers.