CBD vs THC

Definitions

Cannabis contains more than eighty biologically active compounds, and the best known are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). [1] The FDA says THC produces the "high" associated with marijuana, while CBD is a single compound and marijuana is a plant material containing many compounds. [1] NIDA says THC has intoxicating, mind-altering effects. [2] Evidence labels used here: approved medicine, promising but limited, insufficient evidence, evidence of harm, marketing claim. For each compound in depth, see CBD and THC.

Side by side

What the evidence says

Approved uses. Both compounds have FDA-approved medicines, but only for narrow uses. [6] NCCIH adds that some evidence suggests modest benefits of cannabis or cannabinoids for chronic pain and multiple sclerosis symptoms, and that research on other conditions is in early stages. [4] Label: approved medicine for the listed uses; promising but limited for pain and MS symptoms. See approved cannabinoid medicines.

Marketing claims. The FDA has warned companies about CBD products with unproven claims to treat serious diseases, and says unapproved products have not been evaluated for effectiveness, dose or interactions. [1] Label: marketing claim.

Effects and risks

CBD. The FDA identified liver injury during the approved medicine's review and says CBD can affect how other drugs work. [1] In 16 healthy adults given a high study amount for about 3.5 weeks, seven had above-normal liver enzyme readings. [7] NCCIH says CBD may also produce psychotic effects or cognitive impairment in people who also regularly use THC. [4] See medicine interactions and toxicology.

THC. NIDA links heavy use to problems with learning and memory, reports that intoxication can cause a temporary psychotic episode in some people, and says smoke contains many of the same toxins as tobacco smoke. [2] Cannabis use is associated with higher crash risk in a meta-analysis. [8] See pregnancy, teens and driving.

Legal difference

In the US, the 2018 Farm Bill removed hemp, with no more than 0.3% delta-9 THC, from the Controlled Substances Act, but the FDA still regulates products containing it. [6] In the UK, pure CBD is not controlled while THC is a Class B drug, and CBD products often contain traces of THC. [9] Laws change; this is not legal advice. See cannabis laws by country.

No universal winner

Neither compound is "better". CBD avoids the intoxication of THC but has real liver, sedation and interaction concerns, and its consumer products are poorly standardized. THC has approved uses but carries impairment and mental health risks. Which is appropriate for any person is a question for a clinician, and neither should replace approved treatment.