Psilocybin and Cluster Headaches | EDABEA

Psilocybin and cluster headaches (Horton’s syndrome): clinical evidence and research status

Cluster headaches or Horton’s syndrome is one of the most intense documented primary pain syndromes in medicine, characterized by unilateral periorbital pain attacks that can last from 15 minutes to 3 hours and recur several times a day for weeks or months. In Spain, studies by the Cluster Headache Aid Association (ACRA) and the Brain Foundation estimate that approximately 25,000 people are affected, of which about 28% suffer from the chronic form of the disease. The same study notes that patients "are not managed adequately" and documents "the inappropriate preventive treatment regimen" in a significant proportion of cases.

Due to the insufficiency of conventional treatments for some patients, the ACRA study documents that nearly 20% of respondents had used hallucinogenic substances at some point to treat their condition, and 5.4% do so frequently. As Dr. Jesús Porta Etessam notes in the study: "Precisely because of their inadequate treatment and sometimes the lack of response to initial therapies, patients with cluster headaches consider the possibility of turning to unestablished treatments." This clinical reality – patients looking for solutions outside conventional systems due to a lack of effective alternatives – is the context that gives meaning to the research on psilocybin in cluster headaches. To delve deeper into the use of these substances in mental disorders, you can consult our articles on psilocybes for anxiety and depression and on what psilocybin is and what it is used for.

Neuropharmacological Hypothesis

The mechanism by which psilocybin may act on cluster headaches is not fully established, but the most accepted hypothesis in the literature involves serotoninergic receptors 5-HT2B present in intracranial blood vessels and in the caudal trigeminal nucleus – structures involved in the pathophysiology of cluster headaches. Psilocin (the active compound of psilocybin) has documented affinity for multiple subtypes of serotoninergic receptors, including 5-HT2B, which could modulate the vasodilation and trigeminal activation characteristic of the attacks.

A relevant point that reinforces this hypothesis, which several researchers have pointed out: the documented effect in some patients occurs at subpsychedelic doses – below the threshold of hallucinogenic effects – suggesting that the mechanism of action in cluster headaches may be different from the psychedelic effect mediated by the 5-HT2A receptors in the prefrontal cortex.

Dried Psilocybe cubensis. Source: Erik Fenderson, Wikipedia.

Published Clinical Studies

Sewell, Halpern, and Pope (2006)

The first observational studies were conducted by Sewell, Halpern, and Pope, published in 2006 in Neurology under the title "Response of cluster headache to psilocybin and LSD". The study interviewed 53 cluster headache patients who had used psilocybin or LSD to treat their condition. The results documented that psilocybin aborted attacks in 22 of 26 patients (85%) and showed a preventive effect in 90% of reported cases (Sewell, R.A. et al., 2006. Neurology, 66(12), 1920–1922).

As noted by Drs. Sempere, Berenguer-Ruiz, and Almazán in their review "Chronic cluster headache: response to psilocybin," the Sewell study "has evident limitations" – it is observational, retrospective, without a control group, and with possible placebo effect – but it also highlights that "psilocybin has the advantage of having both abortive and preventive effects on cluster headache attacks," and that "the effect of psilocybin occurs at sub-hallucinogenic doses, indicating a different mechanism of action than its psychoactive effects."

Halpern, Karst, Bernateck, and Passie (2010)

In 2010, Halpern and colleagues published in Cephalalgia the study "The non-hallucinogen 2-bromo-lysergic acid diethylamide as preventative treatment for cluster headache: An open, non-randomized case series". This investigation analyzed the effects of 2-bromo-LSD, an analogue of LSD without psychoactive activity, as a preventive treatment for cluster headaches. The goal was to isolate the therapeutic effect of the molecular structure of the compound from its psychedelic activity. The results were positive but insufficient, and the research highlighted the need for controlled trials (Halpern, J.H. et al., 2010. Cephalalgia, 30(9), 1167–1174).

Psilocybe tampanensis. Source: Workman, Wikipedia.

Current Status of Research and Regulatory Barriers

The scientific community agrees that the main obstacle to advancing research on psychedelics in cluster headaches is their classification as controlled substances in most legal frameworks, which limits research protocols, raises the cost of trials, and complicates funding acquisition. This situation, as highlighted by researchers in the field, hampers scientific advancement and postpones the possibility of developing derivative compounds – such as 2-bromo-LSD – that lack psychoactive effect and could be marketed in appropriate therapeutic formulations.

The organization MAPS (Multidisciplinary Association for Psychedelic Studies) continues to fund and coordinate research in this line. The general renaissance of clinical research with psychedelics since 2006 – with the FDA designating psilocybin for treatment-resistant depression as a Breakthrough Therapy in 2018 – has opened a more favorable regulatory context that could also benefit research in cluster headaches in the coming years.

About this content

Article by Nina Slick. Reviewed and updated by the Edabea team. Clinical information is based on the cited bibliographic studies. It does not constitute medical recommendation. Last updated: April 2026.

Bibliographic References

• Halpern, J.H. et al. (2010). The non-hallucinogen 2-bromo-lysergic acid diethylamide as preventative treatment for cluster headache. Cephalalgia, 30(9), 1167–1174.
• Sewell, R.A., Halpern, J.H. & Pope, H.G. (2006). Response of cluster headache to psilocybin and LSD. Neurology, 66(12), 1920–1922.
• Sempere, A.P., Berenguer-Ruiz, L. & Almazán, F. Chronic cluster headache: response to psilocybin. Neurology Service, General University Hospital of Alicante.