Headache is one of the most common reasons people give for using cannabis medically, and it is one of the least well studied.
This post covers the proposed mechanism, the trial evidence that exists, the specific trap that catches long-term users, and where the limits of current knowledge are. For background on the endocannabinoid system itself, see topic 1306.
This post is educational. It is not a recommendation to treat migraine with cannabis. If you have migraine or cluster headache, see a neurologist.
The hypothesis: clinical endocannabinoid deficiency
The theoretical case for cannabinoids in headache rests on Ethan Russo’s “clinical endocannabinoid deficiency” idea, revisited in a 2016 review. It proposes that some treatment-resistant conditions, including migraine, share a low endocannabinoid tone, and CB1 receptors are present in structures involved in migraine. It remains a hypothesis, not an established mechanism. Treat it as a reason to run trials, not as a reason to conclude the trials would succeed. The mechanism is covered in more depth in topic 1306 and bai176.
The trial evidence
There is now one properly designed randomised controlled trial of cannabis for acute migraine. It is worth knowing in detail because almost everything else in this field is survey data.
The trial was led by Nathaniel Schuster at UC San Diego and published in Headache in 2026 (online December 2025). It used a randomised, double-blind, placebo-controlled crossover design. Participants treated up to four separate acute migraine attacks, at least one week apart. Each attack got a different randomly assigned treatment of vaporised flower from one of four arms.
92 participants were enrolled and randomised, and 247 migraine attacks were treated.
The four arms:
| Arm | Nominal content |
|---|---|
| THC-dominant | 6% THC |
| CBD-dominant | 11% CBD |
| THC + CBD | 6% THC + 11% CBD |
| Placebo | no THC or CBD |
Primary endpoint: pain relief at 2 hours
| Arm | Pain relief at 2 h | Statistics vs placebo |
|---|---|---|
| THC-dominant | 68.9% | OR 3.14 [1.35–7.30], p = 0.008 |
| THC + CBD | 67.2% | OR 2.85 [1.22–6.65], p = 0.016 |
| CBD-dominant | — | not superior to placebo |
| Placebo | 46.6% | — |
Secondary endpoints at 2 hours, where the arms separate:
| Endpoint | THC + CBD | Placebo | Statistics |
|---|---|---|---|
| Pain freedom | 34.5% | 15.5% | OR 3.30 [1.24–8.80], p = 0.017 |
| Most bothersome symptom (MBS) freedom | 60.3% | 34.5% | OR 3.32 [1.45–7.64], p = 0.005 |
The THC-dominant arm did not beat placebo on either of these two endpoints, and the CBD-dominant arm did not beat placebo on any endpoint. Only the combination did.
Sustained benefit: again only the combination. The THC + CBD arm was superior to placebo for sustained pain freedom at 24 hours and for sustained MBS freedom at 24 and 48 hours.
Adverse effects. No serious adverse events occurred in any arm. In the earlier preprint, mean self-rated “highness” at one hour was 3.5/10 for THC-dominant and 2.4/10 for THC + CBD. Check the published paper for the final figures.
How to read this. On the primary endpoint, the THC-only arm and the combination arm look much the same: both gave roughly 68% pain relief, against 47% for placebo. But the combination was the only arm that produced pain freedom, symptom freedom and sustained benefit at 24 and 48 hours. It also appears to have done so with less subjective intoxication than THC alone. In this trial, adding CBD did not dilute the benefit.
Note also the placebo numbers: 46.6% pain relief and 15.5% pain freedom on placebo. That is a large placebo response. It is normal in migraine trials, and it is exactly why uncontrolled reports of cannabis working for headache tell you so little.
Limitations. The trial tested only THC and CBD, without minor cannabinoids or terpenes. It used single potencies, one THC:CBD ratio and inhaled flower. It did not assess repeated or long-term use, so it says nothing about medication overuse headache risk, cannabis use disorder or prevention.
What the trial does not cover: there are no randomised controlled trials of cannabis for migraine prevention. Acute treatment and prevention are different questions with different evidence requirements, and only one of them has been tested.
Cluster headache has no randomised controlled trials of cannabis. The survey data that exists is not encouraging. In a French study of 139 cluster headache patients (Leroux et al., Cephalalgia, 2013), 27 had tried cannabis for acute attacks. About a quarter reported some benefit, about half reported variable or uncertain effects, and about a fifth reported that it made things worse. The authors concluded its efficacy for attacks is limited. Anyone telling you cannabis is evidenced for cluster headache is extrapolating.
The trap: medication overuse headache
This is the part of the subject that gets the least attention and deserves the most.
Medication overuse headache is a well-established clinical entity. Frequent use of acute headache medication can turn episodic headache into chronic daily headache. This applies to triptans, combination analgesics, opioids, and even simple painkillers past a certain frequency. The treatment becomes the cause. Patients typically do not recognise it, because from the inside it looks like the condition getting worse and needing more medication.
Whether cannabis does this is an open question. The 2024 review in Practical Neurology puts it plainly: “No RCTs have been performed to study cannabis for migraine prevention, and additional studies are needed to evaluate whether cannabis use contributes to medication overuse headache in some individuals.”
So the current state of knowledge is this: cannabis plausibly could cause medication overuse headache, nobody has established whether it does, and nothing known so far rules it out.
The practical advice does not depend on settling that question. Track your frequency. The International Classification of Headache Disorders (ICHD-3) defines medication overuse headache as headache on 15 or more days a month in someone with a pre-existing headache disorder. It must also involve regular overuse of acute medication for more than three months. Overuse means use on 10 or more days a month for triptans or combination analgesics, or 15 or more days a month for simple analgesics such as paracetamol or NSAIDs. No threshold has been defined for cannabis. If you are treating headaches on that many days with anything, cannabis included, discuss it with a neurologist. A headache diary recording days with headache and days with treatment is the single most useful thing a patient in this situation can produce, and it costs nothing.
A related phenomenon is cannabinoid hyperalgesia. Heavy, long-term cannabinoid exposure can, in some contexts, increase rather than decrease pain sensitivity. This is described in the general pain literature, but whether it matters for headache specifically is not established.
A note on older advice
Much pre-trial advice on cannabis for migraine was reasonable in places. It said the evidence was mostly animal studies, that some patients got worse, and that people should start low. But it often pointed readers to strain-recommendation websites, which are aggregated user reports, not clinical evidence. The trial data suggests the variables that matter are cannabinoid content and ratio, not the cultivar name.
Where this leaves a patient
For acute attacks: there is now one randomised controlled trial. It showed benefit for vaporised THC and, more consistently across endpoints, for THC combined with CBD, with less intoxication from the combination. That is real evidence, and it is one trial.
For prevention: no controlled evidence exists.
For cluster headache: no controlled cannabis evidence exists, and survey results are inconsistent or negative.
On frequency: the risk of medication overuse headache is unresolved for cannabis but established for comparable acute treatments. How often you use it is the thing to monitor.
On combination: one trial, using fixed potencies of inhaled flower, suggests that CBD alongside THC may reduce intoxication without losing efficacy for acute attacks. That is not enough to recommend any product. Discuss it with your doctor.
This is not a migraine treatment recommendation. Anyone with migraine or cluster headache should be assessed by a neurologist.
The Thai legal position (as of October 2026)
Under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568, issued 26 June 2025, cannabis flower is a controlled herb. Key points:
- Flower may be dispensed only against a prescription on form ภ.ท. 33 (PT 33) from an authorised practitioner.
- Each prescription covers no more than 30 days and is single use (no refills).
- Flower that is sold or exported must come from a GACP-certified cultivation site.
- No online sale or advertising of flower, and no recreational use.
Which professions count as authorised practitioners is set by the notification and related rules. Check the current list with the Department of Thai Traditional and Alternative Medicine rather than relying on lists circulated online. Reports also differ on whether the notification names specific indications. Your prescribing practitioner is the right person to ask.
2026 updates. Two Ministerial Regulations B.E. 2569 tightened licensing. One covers cannabis/hemp extracts and has been in force since 26 April 2026. The other, on controlled-herb licences (No. 2), has been in force since 30 April 2026. They do not change the PT 33 prescription rules (see bai209 and bai210). In June 2026 the authorities stepped up enforcement around PT 33 prescriptions (see bai247). The Cannabis Control Act is still a draft: the Cabinet approved it on 22 September 2026 and sent it to the House. For the overall picture, see topic 1330.
Sources: Schuster NM, Wallace MS, Marcotte TD, et al., “Vaporized cannabis versus placebo for acute migraine: A randomized, double-blind, placebo-controlled crossover trial”, Headache: The Journal of Head and Face Pain, 2026;66(2):365–376 (published online 30 December 2025), doi:10.1111/head.70025; earlier preprint: medRxiv 2024, doi:10.1101/2024.02.16.24302843. Leroux E, et al., “Use of cannabis among 139 cluster headache sufferers”, Cephalalgia, 2013, doi:10.1177/0333102412468669. Headache Classification Committee of the International Headache Society, ICHD-3, section 8.2 Medication-overuse headache. “Cannabinoids and Psychedelics for Headache Management”, Practical Neurology, May–June 2024. Russo, “Clinical Endocannabinoid Deficiency Reconsidered”, Cannabis and Cannabinoid Research, 2016. Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis) B.E. 2568.