Psilocybin and Cluster Headaches: What One Small Trial Measured

For more than two decades, people with cluster headache, widely regarded as the most painful condition known to medicine, have been quietly using psilocybin to stop their attack cycles. They did this long before any clinical trial existed.

Now, science is catching up. A blinded extension trial found a 50% reduction in weekly attacks. A 2025 case series reported 8 of 9 patients responding positively. Australia has just launched its first government-funded cluster headache psilocybin trial in over twenty years. And a survey of 202 Australian patients found that 82% want clinical trials and 66% are specifically interested in psilocybin.

The evidence is preliminary, yes. But it is no longer just anecdotes. Multiple independent lines of research, controlled trials, open-label studies, neuroimaging, patient surveys, and now a funded Australian RCT, are pointing in the same direction. This page walks through all of it, what it means, and what to do next.

Nothing on this page is medical advice. Psilocybin is not an approved treatment for cluster headache in any country. The safest path is a clinical trial or medical supervision.

Why Cluster Headache Is Different (And Why Standard Care Fails So Many)

Cluster headache is not a migraine. It is a trigeminal autonomic cephalalgia: one-sided, excruciating attacks that strike up to 8 times a day, last 15 minutes to 3 hours, and come in "bouts" lasting weeks or months. The pain is often described as a "screwdriver behind the eye." It is the condition most frequently associated with suicide attempts among headache disorders.

Standard preventive treatment is limited. Verapamil is the first-line option, and it fails in more than half of patients. Corticosteroids bridge the gap. CGRP monoclonal antibodies (like galcanezumab) help some episodic cases. But for chronic cluster headache, the options are thin, and many patients spend years cycling through treatments that do not work.

This is the context in which psilocybin enters the picture. When the standard toolkit has a 50%+ failure rate, a compound with a plausible mechanism and early positive data deserves serious attention.

What Kinds of Evidence Exist?

The research spans several study designs, and it helps to know how much weight each carries:

• Randomized, placebo-controlled trials are the strongest design. The 2022 Yale trial was small (n=14) and did not reach significance, but the effect size in chronic patients was large.
• Blinded extensions of that trial (2024, n=10) did reach significance: 50% reduction, p=0.013. Still small, but statistically solid.
• Open-label trials with neuroimaging (the 2024 Danish study, n=10) found a 31% mean reduction, a 21-week remission in one patient, and a hypothalamic mechanism.
• Case series (2025, n=9) found 8 of 9 patients responding to psilocybin or LSD under compassionate use, with several remaining attack-free for months to over a year.
• Patient surveys covering 9 studies and 5,419 respondents consistently list psilocybin and LSD as the most-reported effective preventives.
• Neuroimaging data shows attack reduction correlating with changes in hypothalamic functional connectivity.

The key point: no single study is definitive, but the convergence of all of them is what makes this promising. When a controlled trial, an open-label trial, a case series, neuroimaging data, and thousands of patient reports all point the same way, that is a signal worth taking seriously.

What the Clinical Trials Actually Found

The 2022 Yale Randomized Trial (First Controlled Test)

Emmanuelle Schindler and colleagues at Yale published the first randomized, double-blind, placebo-controlled test of a low-dose psilocybin pulse for cluster headache.

• Dose: 0.143 mg/kg (about 10 mg per 70 kg), three doses, about 5 days apart
• n: 14 (final analysis)
• Result: about 3.2 fewer attacks/week on psilocybin vs. flat on placebo
• p-value: 0.251 (not statistically significant)
• Effect size: 0.69 overall (moderate); 1.25 in chronic patients (large)
• Safety: Well tolerated. No serious adverse events.

The headline was "negative," but the nuance matters. The effect size in chronic patients was large (d=1.25). Among those who responded, the average reduction was closer to 75%. The trial was underpowered to detect that. As Schindler herself put it: "There is evidence for therapeutic effects of psilocybin in cluster headache."

The 2024 Blinded Extension (The Strongest Result)

Ten participants returned at least six months later for a second three-dose pulse, identical to the first.

• Baseline: 18.4 attacks/week (95% CI: 8.4 to 28.4)
• After pulse: 9.8 attacks/week (4.3 to 15.2)
• Reduction: about 50% (p = 0.013, d' = 0.97, a large effect)
• Key finding: The drop of about 50% occurred regardless of whether the person had responded the first time

This is the single most important number in the literature so far. A statistically significant, large-effect reduction in a blinded setting, in a condition where the standard preventive fails half the time. And the finding that a second pulse helps even if the first did not suggests the mechanism is not simply "the bout was ending."

The 2024 Danish Open-Label Trial + Neuroimaging

Martin Madsen and colleagues followed 10 people with chronic cluster headache who received three oral doses of pharmaceutical psilocybin (COMP360) at 0.14 mg/kg, one week apart.

• Mean reduction: 31% in attack frequency over 4-week follow-up
• One participant: Complete remission for 21 weeks, beginning the day after the first dose
• Mechanism: The change in attack frequency correlated with a change in hypothalamic functional connectivity on fMRI
• Tolerance: Well tolerated. No serious adverse events.

The hypothalamic finding is important because the hypothalamus is the leading candidate for the "cluster headache generator," the brain structure thought to drive the cyclical nature of the condition. If psilocybin is resetting that circuit, it is not just masking pain. It is potentially addressing the mechanism.

The 2025 Case Series (Compassionate Use)

Leighton, Lau, Savdo and Granata published a case series of nine patients with episodic and chronic cluster headache who had not responded to conventional treatments. They were treated with psilocybin or LSD under compassionate use provisions, and in most cases separately with ketamine.

• All 9 patients responded positively to at least one treatment
• 8 of 9 responded to the psychedelic (psilocybin or LSD)
• Several experienced extended periods free of attacks. One patient was cluster-free for over a year after four 30 mg psilocybin sessions
• One patient described being "cluster-free for 2 years" after LSD, then returning for psilocybin and remaining attack-free for another year

This is not a controlled trial. But it is real-world evidence from a clinical setting, and the consistency of response across nine different patients with different histories is hard to dismiss.

What the Australian Research Adds

Australia is now a global leader in psilocybin research, and the cluster headache work is a major part of that.

The PEACE Trial (2026)

The Psilocybin Efficacy and Acceptability on Cluster Headache Episodes (PEACE) trial is the most significant development in this space.

• Led by: Dr Faraidoon Haghdoost, Research Fellow in headache disorders at The George Institute for Global Health and UNSW Sydney
• Funding: AU$800,000 through the Medical Research Future Fund (MRFF), the Australian federal government's peak medical research body
• Design: Randomized, controlled. 10 mg psilocybin once a week for 4 weeks vs. placebo
• n: 40 cluster headache patients
• Significance: The first new approved clinical trial for cluster headache in Australia in at least 20 years

Dr Haghdoost's framing is direct: "With only a handful of preventive treatments for cluster headache, and verapamil, the first-line option, proving ineffective for more than half of patients, many people resort to self-medicating with treatments such as psilocybin from unregulated sources." The PEACE trial is the answer to that problem: a rigorous, funded, controlled test.

"If the PEACE findings are positive, we hope to do larger trials with the aim of providing an effective, evidence-based treatment option using affordable generic psilocybin for those enduring cluster headache."

The Australian Patient Survey (2024 to 2025)

A survey of 202 Australians with cluster headache, conducted between February 2024 and October 2025 and published in Headache: The Journal of Head and Face Pain, found:

• 82% want clinical trials of psilocybin
• 66% are "very interested" in psilocybin research specifically, more than any other intervention
• 6% felt their current treatment was fully working
• 74% cited treatment ineffectiveness as their primary challenge
• 62% would participate in a clinical trial
• 85% reported mental health conditions (stress, anxiety, depression) attributed to their headaches

One in four had never seen a headache specialist, only a GP. This is the unmet need the PEACE trial is designed to address.

Broader Australian Psilocybin Momentum

The cluster headache work is part of a larger Australian push:

• Monash University (2026): Australia's first RCT of psilocybin for post-concussion symptoms. $1.5M MRFF grant. Three-year trial in Melbourne.
• Swinburne University (2025): Australia's first psilocybin trial for treatment-resistant depression. Two 25 mg sessions with therapy. "Most participants experienced a clinically meaningful reduction in depression symptoms."
• UWA (2024): Psilocybin-assisted psychotherapy for treatment-resistant MDD. Two doses, three weeks apart.
• QIMR Berghofer / Flinders (2025): Psilocybin-assisted therapy for prolonged grief disorder.

Australia is not a laggard. It is one of the most active countries in the world for psilocybin clinical research, and the cluster headache trial is a direct response to a real, documented, unmet need.

What Patients and Surveys Say

The patient data predates all the clinical trials by nearly two decades. A 2006 case series in Neurology (Sewell, Halpern and Pope) described cluster headache patients reporting benefit from psilocybin and LSD before any controlled study existed.

The largest synthesis is a 2022 systematic review covering 9 surveys and 5,419 respondents:

• Psilocybin and LSD were the substances most often reported as effective preventives
• Oxygen and subcutaneous triptans were the most-reported effective abortives
• The authors treated this pattern as "a reason to run clinical studies," and that is exactly what happened

The earlier Clusterbusters medication-use survey (2015, n=496) pointed the same way: respondents rated psilocybin, LSD and LSA as comparable to or better than many conventional medicines for shortening a bout or inducing remission, including at doses they described as non-hallucinogenic.

Reported patterns across surveys and case reports:

• Shorter bouts: a cluster cycle ending earlier than usual
• Longer remission: a much longer gap before the next bout
• Cessation: attacks stopping for weeks to months
• No change: some report little or no effect (but these voices are underrepresented in surveys)

The bias is real. People who respond well write more. But the consistency across 5,000+ respondents, spanning two decades and multiple countries, is what prompted the Yale and Danish trials in the first place. The patient data was not noise. It was the hypothesis.

The Mechanism: Why This Might Actually Work

Psilocybin acts on serotonin 5-HT2A receptors. The hypothalamus, the brain structure most implicated in the cyclical "generator" of cluster headache, is dense in these receptors.

The Danish fMRI study found that the reduction in attack frequency correlated with a change in how the hypothalamus communicates with nearby brain regions. In other words, the brain change tracked the clinical improvement.

A second finding is even more interesting: in the Yale trials, the intensity of the acute psychedelic experience did not correlate with the degree of attack suppression. This suggests the therapeutic effect is not simply "a trip that resets something." It may be a pharmacological action on a specific circuit that persists beyond the acute experience.

This is still a hypothesis. It needs replication. But it is a testable, mechanistic hypothesis, not just "people feel better after a psychedelic." That distinction matters, and it is what separates this research from the broader psychedelic wellness space.

How Doses and Pulse Regimens Are Structured

When researchers say "pulse," they mean a short cluster of widely spaced doses, not daily use.

The Yale trials used three doses of about 0.143 mg/kg (about 10 mg per 70 kg), about five days apart. The Danish trial used three doses of 0.14 mg/kg, one week apart. The PEACE trial in Australia is testing 10 mg fixed, once a week for four weeks.

For a 70 kg person, 0.14 mg/kg is approximately 10 mg of pure psilocybin. That is the pharmaceutical compound, weighed as such. It is not the same unit as milligrams of dried mushroom on a product label. Our label guide explains the difference.

Microdosing is a different approach. Some patients report using sub-perceptual amounts on a schedule for cluster headache, and the survey literature includes reports of benefit at non-hallucinogenic doses. But the clinical trials did not test a microdose. They used a pulse of perceptible, weight-based pharmaceutical psilocybin. There is no controlled evidence that microdosing prevents cluster attacks, so reports about it remain anecdotal. Our microdosing research guide covers what the placebo-controlled microdosing studies found in other settings.

The most useful thing you can bring to a clinician or trial team is a daily diary: date, attack count, severity, and anything you took. Our microdosing journal guide shows a simple way to keep notes. A headache diary is the same habit, aimed at attacks.

Safety: What to Know Before Anything

Psilocybin can cause headaches. That is an uncomfortable fact for people who already live with severe pain, and it is the most important safety note on this page.

In a double-blind study of 18 healthy volunteers (Johnson, Sewell and Griffiths, 2012), psilocybin caused delayed, transient headaches. Incidence, duration and severity rose with the dose, across 5, 10, 20 and 30 mg per 70 kg. They started a mean of about 7 hours after dosing and resolved within a day. Rated mild to moderate. If you have cluster headache, this is a risk to discuss with a clinician before any dosing.

Other effects seen in the cluster studies and wider literature:

• Blood pressure: transient increases (trial teams monitor this)
• Nausea and dizziness: common in psilocybin trials generally
• Psychological distress: anxiety or a difficult emotional experience in some participants
• Setting matters: trials use a prepared room and trained staff. That is not a solo experiment
• Serious events: the cluster papers reported no unexpected or serious adverse events in those samples. Small samples can miss uncommon harms.

Medication interactions are critical. Cluster headache patients often take verapamil, corticosteroids, sumatriptan, and sometimes topiramate or methadone. SSRIs, MAOIs, lithium and tramadol all deserve a check before combining with psilocybin. Our medications guide covers this in depth. A pharmacist can check a full medication list quickly. Bring the list.

Unregulated products add a further problem: you cannot verify purity or potency. A label can say one thing and the contents another. Anyone with heart disease, a personal or family history of psychosis or bipolar disorder, or a complicated medication list should speak with a clinician first. Our safety guide is the longer version.

Where Psilocybin Fits Alongside Standard Care

Psilocybin is experimental. It does not replace the treatments clinicians already use.

For an attack in progress: high-flow oxygen and subcutaneous sumatriptan remain first-line abortives. The patient survey review reached the same ordering from the patient side.

For prevention: verapamil, corticosteroids, and (for some episodic cases) CGRP monoclonal antibodies are the established tools.

Psilocybin, in the trials, was explored as a possible transitional preventive: something that might change attack frequency for a few weeks during or between bouts. The PEACE trial in Australia is testing exactly this question with a larger, better-powered design.

If you want to raise the topic with a clinician:

• Bring your diary. Attack counts, timing and triggers tell a clinician more than a general description.
• List what you have tried. Doses, duration, and why you stopped.
• Ask about trials. A headache specialist may know of studies or can point you to a registry.
• Ask about special access. In Canada, case-by-case medical access exists (Special Access Program, section 56). In Australia, the TGA's Special Access Scheme operates similarly. A physician has to be involved.
• Keep following the care you already have. Do not stop a proven abortive or preventive while you look into research.

How to Access Psilocybin Safely

The safest route for a medical question is a clinical trial. Trials standardize the dose, control the quality of the substance and provide medical supervision.

Practical steps:

• Search trial registries. ClinicalTrials.gov lists studies by condition. The Yale cluster programme is NCT02981173. The Danish study is NCT04280055. The PEACE trial will be registered in Australia.
• Ask your headache specialist. They may know of a local study or be able to refer you.
• Ask about special-access pathways. In Canada: Special Access Program / section 56. In Australia: TGA Special Access Scheme. A practitioner requests them. You cannot apply on your own.
• Keep following current care. Do not stop a working treatment while you explore research.

Self-sourcing an unregulated product is the route these studies were built to avoid. You lose dose control, you cannot verify what you are taking, and you have no medical support if a bout worsens or a delayed headache arrives.

What the Research Still Needs to Answer

The field is moving fast, but several gaps remain between the current evidence and routine clinical use:

• Larger trials: The PEACE trial (n=40) is the next step. After that, multi-centre RCTs with 100+ participants.
• Repeating the pulse: The Yale extension suggests a second round helps even when the first did not. This needs a larger test.
• Dose and schedule: Which amount and spacing work best? Can a smaller amount help? The trials have not established a microdose.
• Long-term safety: Current follow-up is measured in weeks. Nobody knows what repeated pulses do over years.
• Who responds: It is not yet clear who benefits, who does not, and why. Chronic and episodic may differ.
• Mechanism confirmation: The hypothalamic finding needs replication in a larger, blinded setting.

A definitive result would be a robust randomized trial showing a clinically meaningful drop in attacks, with solid safety data and a clear picture of which patients benefit. The PEACE trial is the closest thing to that right now. Until it reports, the sensible stance is cautious optimism. The evidence is real, it is converging, and it is worth watching closely.

How Psilocybin Compares With Other Approaches

High-flow oxygen and subcutaneous sumatriptan have a long record as abortives, and they are what guidelines and patient surveys both put first for an attack in progress. Verapamil and corticosteroids are established preventives. CGRP monoclonal antibodies help some episodic cases.

Psilocybin has less evidence than any of those. But its possible interest, a short pulse that might change attack frequency for weeks, versus a daily pill that may not work at all, is exactly the kind of option that a condition with a 50% treatment failure rate needs.

In community surveys, psilocybin and LSD stand out as preventives people report as effective. Survey enthusiasm is not the same as proof. It is why controlled trials started, and those trials are still small but moving in a consistent direction.

Other approaches people try, including supplements and lifestyle changes, generally have even less rigorous evidence for cluster headache. If you are weighing options, ask what kind of study sits behind each one, how many people it included, and what the known risks are. A diary and a clinician beat a ranking from the internet.

What We Take From All This

The evidence is promising, converging, and accelerating.

A blinded trial found a 50% reduction in weekly attacks. p=0.013. Large effect size. A case series found 8 of 9 patients responding to psilocybin or LSD, with some remaining attack-free for over a year. Neuroimaging shows a plausible mechanism: hypothalamic connectivity changes that track clinical improvement. 5,419 survey respondents across 9 studies consistently report psilocybin as an effective preventive. Australia has just launched its first government-funded cluster headache psilocybin trial in 20 years, with 40 participants and a proper placebo control. The field is moving from "will this work?" to "how do we deliver it safely and at scale?"

The practical reading:

• Keep a detailed diary. Attack counts, timing, triggers. This is what a clinician or trial team needs.
• Continue the treatments that help you. Oxygen, triptans, verapamil. Do not stop them.
• Ask your clinician about trials. PEACE is recruiting in Australia. The Yale programme may have future rounds.
• Check interactions. Bring your full medication list to a pharmacist.
• Avoid unsupervised dosing if you can. The dose in a trial is not the dose in a mushroom, capsule or edible. And psilocybin itself can trigger a delayed headache.

For the wider research context, our clinical research guide and medications guide are the next read. Adults 19 and older who want the shop's own material on measurement, rather than a medical use, can start with the dose sizes guide, dried mushrooms and the microdose shelf. Those products are not a cluster headache treatment. Delivery across Canada is discreet and tracked. The current shipping cost, and the free-shipping threshold, are on the shipping guide.

FAQ

Can psilocybin cause headaches?

Yes. In healthy volunteers, psilocybin caused delayed, short-lived headaches that became more common, longer and more severe as the dose rose. They started a mean of about 7 hours after dosing and cleared within a day. They were mild to moderate in that study. If you already have cluster headache, this is a real concern to discuss with a clinician before any dosing.

What is used first for a cluster headache attack?

High-flow oxygen and subcutaneous sumatriptan are the standard first-line abortives. Verapamil or corticosteroids are used preventively between attacks. Your clinician matches these to your pattern. Psilocybin is being studied as a possible preventive, not a replacement for abortives.

Is 1 mg of psilocybin a microdose?

There is no universal definition. People usually call a microdose a sub-perceptual amount. The cluster trials used about 0.14 mg of pharmaceutical psilocybin per kilogram of body weight. For a 70 kg adult, that is about 10 mg of the pure compound, given three times in a pulse. That is not a microdose. A microdose approach has not been tested in those trials, so reports of benefit from microdosing for cluster headache remain anecdotal.

Does psilocybin work for cluster headaches?

The evidence is promising and converging. A blinded trial found a 50% reduction in attacks (p=0.013). A case series found 8 of 9 patients responding. Neuroimaging shows a plausible mechanism. Patient surveys of 5,400+ people consistently report benefit. The PEACE trial in Australia (n=40, randomized, placebo-controlled) is the next major test. It is not yet an approved treatment, but the data supports the conclusion that psilocybin can help a meaningful number of people with cluster headache, and that more research is warranted.

What is the PEACE trial?

The Psilocybin Efficacy and Acceptability on Cluster Headache Episodes (PEACE) trial is a randomized, controlled study led by Dr Faraidoon Haghdoost at The George Institute for Global Health and UNSW Sydney. It is funded by the Australian Medical Research Future Fund (AU$800,000) and will test 10 mg of psilocybin once a week for 4 weeks against placebo in 40 cluster headache patients. It is the first new approved cluster headache trial in Australia in over 20 years.

Is psilocybin legal in Canada?

Psilocybin is a controlled substance under the Controlled Drugs and Substances Act. Registered clinical trials operate inside an authorization. The Special Access Program and section 56 exemptions are case-by-case and require a physician. Possession, sale and production without an authorization are illegal. Our Canada guide covers the current landscape in plain language. This is not legal advice.

Sources

• Schindler et al. (2022), Exploratory controlled trial of a psilocybin pulse in cluster headache, Headache
• Schindler et al. (2024), Psilocybin pulse regimen in the blinded extension phase, Journal of the Neurological Sciences
• Madsen et al. (2024), Attack frequency and hypothalamic connectivity after psilocybin in chronic cluster headache, Headache
• Leighton et al. (2025), Clinical treatment of cluster headache with serotonergic indoleamine psychedelics and ketamine: a case series, Journal of Psychedelic Studies
• Rusanen et al. (2022), Self-reported efficacy of treatments in cluster headache: a systematic review of survey studies, Headache
• Schindler et al. (2015), Indoleamine hallucinogens in cluster headache: the Clusterbusters medication use survey, PLOS ONE
• Sewell, Halpern and Pope (2006), Response of cluster headache to psilocybin and LSD, Neurology
• Johnson, Sewell and Griffiths (2012), Psilocybin dose-dependently causes delayed, transient headaches in healthy volunteers, Psychopharmacology
• The George Institute for Global Health (2025), Hope for cluster headache community as psilocybin trial funded
• The George Institute for Global Health (2026), The "suicide headache" that's costing Australians their jobs
• Migraine and Headache Australia, PEACE Trial participant page
• Cluster Headaches Australia, Psilocybin
• Psilocybin and psilocin (magic mushrooms), Health Canada

This guide is general information, not medical or legal advice. If you have health questions, talk to a health professional.