Psilocybin and cluster headache: what the studies actually found

Cluster headache is rare, but people who have it often describe it as the worst pain they know. Over the past two decades, some of them have reported that psilocybin, the compound in magic mushrooms, made their attacks stop or their cluster periods end early. Researchers took those reports seriously enough to run trials.

This page sets out what those studies did and found, including results that were not statistically significant. It describes research only. It does not say what anyone should take or do, and it gives no amounts. If you have headaches like the ones described here, the right first step is a doctor, because established treatments exist.

What is cluster headache?

The US National Institute of Neurological Disorders and Stroke (NINDS) describes cluster headache as the most common type of trigeminal autonomic cephalalgia, and says it “can also be the most severe type of primary headache” (NINDS). Attacks come in series called cluster periods, from every other day to eight times a day. The pain is usually on one side, behind or around one eye, peaks within five to 10 minutes and can last up to three hours. The eye and nose on that side may redden, swell or water, and attacks often wake people from sleep (NINDS).

Most people have cluster periods separated by months without symptoms, which is the episodic form. A small group develop a chronic form, with cluster periods that can go on for years with only short pain-free times (NINDS). In a survey of 1,604 people who rated their attacks against other painful conditions they had experienced, the authors concluded it is intensely painful “even in the context of other disorders considered intensely painful” (Burish et al., 2021).

Standard treatments exist

This matters for everything that follows. NINDS says most doctors recommend verapamil as the first choice for preventing cluster periods, and lists oxygen therapy, triptans, lidocaine, ergots and octreotide among other treatments (NINDS). The UK’s National Health Service (NHS) says ordinary painkillers such as paracetamol and ibuprofen do not work for cluster headache, and lists triptan injections or nasal sprays, oxygen and nerve stimulation for attacks, and corticosteroids, verapamil or lithium for prevention (NHS).

Those treatments have real limits. A 2023 consensus article by European headache specialists said preventive treatment is “sparsely studied” and limited by low efficacy and side effects, and that there is a “great and unmet need” for better options (Lund et al., 2023).

Where did the idea come from?

From patients. In 2006 three researchers, R. Andrew Sewell, John Halpern and Harrison Pope, published a short report in the journal Neurology. They interviewed 53 people with cluster headache who had used psilocybin or LSD to treat it themselves (Sewell, Halpern and Pope, 2006).

• 22 of 26 psilocybin users said it stopped attacks once they had started.
• 25 of 48 psilocybin users, and 7 of 8 LSD users, said it ended a cluster period.
• 18 of 19 psilocybin users, and 4 of 5 LSD users, said it lengthened the time between cluster periods.

The authors concluded only that research “may be warranted” (Sewell, Halpern and Pope, 2006). That caution is right. These were self-reports from people who chose to try a drug and were willing to talk about it. There was no comparison group and no check on what they took. People for whom it did nothing were less likely to come forward. A report like this is a reason to run a trial, not evidence that something works.

The role of patient advocacy: Clusterbusters

Clusterbusters is a patient organization. Its online medication use survey was analysed by researchers including Sewell. The final analysis included 496 people recruited from cluster headache websites and headache clinics. Respondents rated psilocybin, LSD and a related compound as comparable to, or more effective than, most conventional medicines, and said they shortened cluster periods more often (Schindler et al., 2015).

A second look at the same survey’s free-text comments, from 493 adults, found that 24.7% wrote that “nothing worked” and 35.5% mentioned using illicit substances to manage the condition (Schindler et al., 2021). A 2022 systematic review of nine survey studies (5,419 respondents) found psilocybin and LSD were the most commonly reported effective preventive treatments, while oxygen and triptan injections were most often reported effective for stopping attacks (Rusanen et al., 2022).

The surveys say something real about how hard many people find cluster headache to manage. They share the same weaknesses as the 2006 report: self-selected respondents, self-reported outcomes and no controls.

What did the Yale trials find?

Yale University ran the first placebo-controlled trial, at the VA Connecticut Healthcare System. The registry lists it as a randomized, triple-masked study with a crossover design and 25 people enrolled, and many outcomes, including changes in attack frequency, intensity and duration (ClinicalTrials.gov NCT02981173). The design copied what patients reported: a “pulse” of three sessions about five days apart, with headache diaries kept from two weeks before to eight weeks after the first session (Schindler et al., 2022).

First round, 2022: the main result was not significant

Fourteen people were included in the final analysis, which compared psilocybin with a placebo capsule. In the three weeks after the pulse began, weekly attacks changed by 0.03 with placebo and by −3.2 with psilocybin. The difference was not statistically significant (p = 0.251). The authors wrote plainly that “efficacy outcomes were negative,” owing in part to the small number of participants (Schindler et al., 2022).

They also reported a moderate effect size overall, small in people with episodic cluster headache and large in those with the chronic form. Splitting an already tiny group like this is exploratory and can easily mislead, which is why it needs testing in a larger trial. Psilocybin was well tolerated, with no unexpected or serious adverse events, and the change in attacks was not linked to how strong the acute drug effects felt (Schindler et al., 2022).

Repeat round, 2024: fewer attacks, but no placebo group

Eligible participants could return at least six months later for a repeat pulse of psilocybin in what the authors call a blinded extension phase. Ten completed it. Weekly attacks fell from 18.4 at baseline to 9.8 in the three weeks after the pulse began, a statistically significant drop (p = 0.013) of about 50%, whatever a person’s response in the first round. Again there were no unexpected or serious adverse events (Schindler et al., 2024).

That is a before-and-after comparison within one small group. Without a placebo arm in that round, it cannot separate the drug from the natural ups and downs of cluster periods, expectation or regression to the mean. The authors themselves call for larger, more representative studies over longer periods (Schindler et al., 2024).

What did other headache studies find?

In Denmark, a team at Rigshospitalet in Copenhagen ran an open-label study of psilocybin in chronic cluster headache. It was registered to include more patients but was stopped because the planned number could not be reached during the COVID-19 pandemic (ClinicalTrials.gov NCT04280055). Ten patients kept diaries for 10 weeks. Attack frequency fell by an average of 31% from baseline to follow-up, and one person had 21 weeks of complete remission. The change in attacks correlated with changes in brain connectivity around the hypothalamus on MRI scans (Madsen et al., 2024). A follow-up analysis of 11 patients from the same research programme reported better self-rated sleep after psilocybin, but no statistically significant average change in brain microstructure (Brendstrup-Brix et al., 2026).

In the UK, at King’s College London (ClinicalTrials.gov NCT04905121), a small open-label study tested psilocybin with psychological support in a related rare condition, short-lasting unilateral neuralgiform headache attacks (SUNHA). It stopped early because of recruitment problems: four people enrolled and three completed it. Headache impact stayed severe throughout, attacks fell by more than half in two people, and the authors concluded the results “provide no conclusive evidence” for psilocybin in SUNHA (Rucker et al., 2024).

Migraine trials as context

Yale also tested psilocybin in migraine, a different and far more common headache disorder. In a 2021 crossover study, 10 people were analysed. Weekly migraine days fell by 1.65 in the two weeks after psilocybin, compared with 0.15 after placebo, a significant difference (p = 0.003) (Schindler et al., 2021).

The follow-up trial, published in 2026, used a better comparison. Instead of an inactive capsule, the 18 participants who did not get psilocybin in a given session got diphenhydramine, an antihistamine that causes noticeable effects, so that people would find it harder to tell which they had received. This time the difference among groups was not significant (p = 0.102), and similar reductions of about 50% in migraine frequency were seen in all groups over eight weeks, including the placebo group. Blinding was incomplete, and the authors said future studies need careful planning to separate drug and non-drug effects (Schindler et al., 2026).

That second result is a useful warning for cluster headache research too. When the placebo looked more like the real drug, the advantage seen in the first small trial was no longer clear. For more on why placebo design matters, see our look at microdosing trials and psilocybin depression trials.

A population study adds another kind of evidence. Among 11,419 people in a British cohort, lifetime use of classic psychedelics was linked to 25% lower odds of having frequent bad headaches (Bjurenfalk et al., 2025). Cross-sectional data like this can show an association but not cause.

The studies side by side

Which trials are registered now?

We searched ClinicalTrials.gov on 20 October 2026 for psilocybin in cluster headache, migraine and headache. The two cluster headache psilocybin trials listed are the completed Yale study and the stopped Danish study. We found no psilocybin headache trial listing a site in Canada. Registry entries are written by sponsors and may be out of date.

So the next controlled results in cluster headache may come from LSD, not psilocybin. For how trials in Canada are approved and listed, see our guide to psilocybin clinical trials in Toronto.

What are the safety concerns?

• Headache itself. In a double-blind study of 18 healthy volunteers, psilocybin frequently caused headaches, which became more common, longer and more severe as the dose rose. They started late, were transient and lasted no more than a day (Johnson, Sewell and Griffiths, 2012).
• General effects. Health Canada says magic mushrooms may make people see, hear or feel things that are not there, and lists effects including numbness in the face and increased heart rate and blood pressure (Health Canada).
• Heart and medicines. Specialists note that some standard cluster headache drugs, such as verapamil and triptans, already need cardiac caution and follow-up (Lund et al., 2023). Trials screened people carefully; their safety findings do not cover people with conditions or medicines the trials excluded.
• Uncontrolled products. A 2025 review noted continuing concerns about systemic and psychiatric effects across different doses, preparations and settings, and said more studies are needed before psychedelics can be recommended (Im and Sandoe, 2025).
• Small numbers. The trials above had 4 to 25 people. Studies that size cannot detect uncommon harms.

Is psilocybin an approved headache treatment in Canada?

No. Health Canada’s page (page details dated 20 October 2026) says production, sale and possession of magic mushrooms are illegal in Canada, and that “there are no approved therapeutic products containing psilocybin in Canada or elsewhere.” It calls clinical trials the most appropriate way to research unapproved drugs such as psilocybin, and describes the Special Access Program, through which health care practitioners, not patients, can request access, with no guarantee of approval (Health Canada).

What is still unknown?

• Whether psilocybin reduces cluster attacks more than a well-matched placebo. The only randomized result in cluster headache was not significant.
• Whether episodic and chronic cluster headache respond differently. The hint came from a subgroup of a 14-person trial.
• How long any effect lasts, and what repeating it does over years.
• How much comes from expectation. The 2026 migraine trial showed large improvements in the placebo group once the placebo was harder to tell apart.
• Safety in people with heart disease, on standard cluster medicines, or with the psychiatric conditions trials exclude.

The fair summary: patient reports were striking, the first controlled tests were small and mixed, and the question is still open. For background, see what psilocybin is, our overview of what research shows about psilocybin benefits, and another condition with small early studies, psilocybin and OCD.

Shroomverse sells mushroom products. This article is general information about headache research. It is not medical, legal or purchasing advice, and it does not recommend any product.