CBD: Strong Evidence for Rare Epilepsies, Weak Everywhere Else
Prescription cannabidiol cuts seizures in three rare epilepsies, shown in randomized trials that have been replicated. The oils and gummies sold for pain, sleep, and everyday wellness rest on far less evidence.
CBD, cannabidiol, is one of the two main compounds in the cannabis plant; unlike THC, it doesn't make you high. It comes in two forms people treat as one product. Prescription cannabidiol (Epidiolex) is a purified pharmaceutical liquid, made to a known strength and tested in randomized trials, approved for specific rare epilepsies. Over-the-counter hemp CBD, the oils, gummies, capsules, and creams sold as supplements, is held to no such manufacturing standard and carries almost none of the trial evidence people assume it does.
The strong evidence sits with three rare epilepsies. In Dravet syndrome, a trial of 120 children cut monthly convulsive seizures by about 39%, versus about 13% on placebo; trials in Lennox-Gastaut syndrome and tuberous sclerosis complex found comparable reductions. Below that, a single 300 mg dose lowered acute anxiety before a simulated public-speaking test in small experiments, while 150 mg and 600 mg did not: only the middle dose worked. This is a single-dose laboratory finding; whether a daily gummy treats an anxiety disorder over months has not been tested. For chronic pain and sleep, the two uses CBD is sold for most, the evidence is thin: the best current review found any pain benefit small, and most of the sleep data comes from uncontrolled reports where sleep improved alongside lower anxiety; those reports don't isolate a direct effect on sleep itself.
Retail products deliver a fraction of the doses used in the trials that produced the strong results (the epilepsy trials used 10 to 20 mg per kilogram of body weight a day; a typical gummy delivers 10 to 25 mg total). Cannabidiol is broken down by, and inhibits, the CYP450 liver enzymes that clear many common drugs, so it can raise the blood levels of medicines like anti-seizure drugs and blood thinners; check with a pharmacist before starting it alongside any prescription. The over-the-counter market is poorly regulated: when 84 online CBD products were tested, fewer than a third were labeled accurately for CBD content, and THC was detectable in about one in five, so a recent third-party Certificate of Analysis is the main quality check available.
For the three approved epilepsies, prescription cannabidiol is used under a neurologist, with liver-enzyme monitoring and dose adjustment for interacting drugs built in, a medical decision distinct from buying an oil. For situational anxiety, the evidence points to a single moderate dose taken before a specific stressor; trials have not tested a daily routine. For chronic pain and sleep, the current data doesn't support a reliable effect, so the free groundwork on those specific conditions does more for most people than a supplement.