CBD (Cannabidiol): What It Is, What Research Shows and Safety

Overview and classification

CBD (cannabidiol) is a compound found in the cannabis plant. It is marketed in supplements, foods, oils and lotions. Unlike THC, it is not intoxicating, but it can cause side effects such as drowsiness, decreased appetite, vomiting and diarrhea. [1] The FDA says CBD is a single compound, while marijuana is a plant that contains many compounds, including CBD and THC. [2]

A 2018 WHO expert review found no evidence of abuse or dependence potential for CBD in humans and described it as generally well tolerated. It noted that adverse effects may come from interactions with a person's existing medicines. [3] In a 2020 consumer update, the FDA says the limited safety data it has seen point to real risks, covered below. [2]

Evidence labels used on this page: approved medicine, promising but limited, mixed, insufficient evidence, preclinical (cells/animals only) and marketing claim.

Where it comes from

CBD is a natural cannabinoid formed from its acid precursor, CBDA, by decarboxylation, and it can also be made synthetically. [3] In US federal law, hemp is cannabis with no more than 0.3 percent delta-9 THC on a dry weight basis. [4] The FDA says that even after the 2018 Farm Bill removed hemp from the definition of marijuana, CBD products are still subject to the same laws as other FDA-regulated products. [2] For chemistry see cannabis chemistry.

Regulatory category (as read from regulators)

What research shows, by use

See also cannabis for pain and sleep and neurological conditions research.

Risks, adverse effects and interactions

• Liver injury. The FDA says CBD can cause liver injury. [2] The prescription label requires liver tests before starting and warns that the risk is higher with valproate. [9]
• Other medicines. The FDA says CBD can affect how other drugs work, potentially causing serious side effects. [2] See how interactions work and CBD and cannabis interactions.
• Sedation. Using CBD with alcohol or other drugs that slow brain activity increases the risk of sedation and drowsiness, which can lead to injuries. [2]
• Mood and appetite. The FDA also lists diarrhea or decreased appetite, and irritability or agitation; these should improve when CBD is stopped or reduced. [2]
• Numbers from the approved medicine. In controlled studies of the prescription product, 32 percent of treated patients had somnolence or sedation versus 11 percent on placebo, and 46 percent of treated patients who were also taking clobazam. [9] These figures apply to that medicine under medical supervision, not to store products.
• Animal findings. The FDA notes male reproductive toxicity in animal studies; whether this happens in humans is not known. [2]
• Does CBD turn into THC? The WHO review found no evidence that oral CBD converts to THC in humans. [3]
• What is unknown. The FDA lists unanswered questions, including daily long-term use, which amounts trigger known risks, how consumption methods differ, and effects on the developing brain. [2]

Special groups

• Pregnancy and breastfeeding. The FDA lists effects on the developing fetus or breastfed newborn as unknown. [2] The prescription label says animal data suggest it may cause fetal harm, and that there are no data on human milk. [9] See pregnancy and breastfeeding.
• Children. The FDA lists effects on the developing brain as unknown. [2] The prescription medicine is approved from age 1 for the seizure disorders above. [9]
• Liver disease. The label recommends dosage adjustment in moderate or severe hepatic impairment. [9] See liver safety.
• Mood. The label tells prescribers to monitor for new or worsening depression and suicidal thoughts with this class of medicine. [9]

Quality and labeling concerns

The FDA tested the chemical content of some products and found many did not contain the CBD level claimed; it is also investigating reports of unsafe levels of contaminants such as pesticides, heavy metals and THC. [2] NIDA reports that some products marketed as CBD contain THC. [1] See product forms and labels and certificates of analysis.

Related guides

CBD vs THC and approved cannabinoid medicines.