CBD and migraine: what the first controlled trial found

Migraine is not just a worse headache. It is a neurological disease that comes in attacks. According to the Inserm report on migraine, about 15% of the population is affected, 20% of women and 10% of men. Without effective treatment, an attack lasts 4 to 72 hours.

Tension-type headache is more common. The pain is diffuse and steady, not throbbing, and comes without nausea. Inserm notes that migraine-specific treatments do not work on it. Any study that mixes the two kinds of pain gives results that are hard to read.

A third picture matters here: medication-overuse headache. It develops when a person with migraine takes painkillers too often, and turns into an almost daily pain. Managing it means stopping the medicine involved, sometimes in hospital. Adding one more product to already frequent use moves in the wrong direction.

Before this study, no randomised trial had tested a cannabinoid against an acute migraine attack, the authors note. The team at the University of California San Diego enrolled 92 adults with migraine. Each treated up to four attacks, one with each product, in random order and without knowing which one they had: a vaporised flower with 6% THC, one with 11% CBD, a blend of the two, or a placebo flower. The dose was taken within four hours of the start of the attack, in four inhalations, with at least one week between two treated attacks. In total, 247 attacks were treated. The study was funded by the Migraine Research Foundation and the US National Institutes of Health (NIH).

The main endpoint was the share of attacks where pain, moderate or severe at the start, had dropped to mild or none after two hours.

Several points limit what this result means for a French consumer. CBD was tested by vaporising a flower, not as an oil or a capsule. The "CBD" flower itself contained 0.35% THC, slightly above the French limit. Each participant treated only one attack per product. Above all, the two arms that worked contained 6% THC: the decree of 30 December 2021 caps Δ⁹-THC in authorised hemp at 0.30%, and a flower at 6% is a controlled drug. Our article on the legal THC level explains this threshold.

Researchers are interested because of the endocannabinoid system, a network of receptors involved in passing on pain signals. That is a reason to do research, not proof that anything works.

The other data are weaker. A review published in 2022 in Frontiers in Neurology pooled 12 publications and 1,980 participants in Italy and the United States. Most concerned medical cannabis containing THC, often in studies without a control group. The authors find the results promising but call for well-designed trials. They also flag an unfavourable signal: one study they cite found medication-overuse headache in 81% of people with migraine who used medical cannabis, against 41% of non-users. That is an association, not proof that cannabis causes it.

A 2020 study in the Journal of Pain analysed 12,293 sessions logged in a tracking app for headache, and 7,441 for migraine. Users reported pain roughly halved after inhaling cannabis. There was no placebo and no check on the product, and the effect seemed to fade over time, with doses rising. These figures describe what people report, not what the molecule does.

None of these studies looks at a THC-free CBD oil, the product sold in French shops.

MILDECA points out that products containing CBD may not make therapeutic claims, on pain of criminal penalties, unless they have been authorised as medicines. Article L5111-1 of the French Public Health Code defines as a medicine any product presented as having curative or preventive properties. An oil sold "for migraine" would therefore be an unauthorised medicine.

The only cannabidiol medicine authorised in France is Epidyolex, prescribed for rare childhood epilepsies. Migraine is not one of its indications. Our article on CBD and pain sets out what the legal framework allows anyone to say on the subject.

CBD is cleared by the liver, by the same enzymes as many medicines. The Epidyolex summary of product characteristics, published by the European Medicines Agency, states that it inhibits the CYP2C19 enzyme and can therefore raise blood levels of other drugs. Our article on the grapefruit effect explains this mechanism.

For a person with migraine, three simple rules follow:

• do not stop or space out a prescribed preventive treatment to replace it with CBD;
• tell your doctor or pharmacist about any CBD product, as you would a food supplement;
• see a doctor if attacks change in pattern, become more frequent, or if you take painkillers more than a few days a week.