[Peter Singer] Legalize psychedelic pain relief

John Stuart Mill wrote “On Liberty” to defend the principle that the only justification for restricting liberty is to prevent harm to others. Were Mill alive today, he would have been pleased to see how many jurisdictions have repealed laws criminalizing acts widely thought immoral despite harming no one directly: suicide — including medically assisted dying — is one prominent example. Same-sex relations between consenting adults are another.

In contrast, laws that criminalize potentially self-harming behavior, like traveling in a car without wearing a seatbelt or riding a motorcycle without a helmet, have proliferated. If Mill had been updated with information about how often we fail to give proper weight to low risks of catastrophic outcomes, he might have accepted those laws, while still arguing for exemptions for people who have a serious reason not to wear a seatbelt or a helmet.

This brings me to the issue that has prompted these “What would Mill do?” thoughts: the overwhelming case for exemptions to laws prohibiting certain drugs.

Consider cluster headache, possibly the most painful condition known to medicine. It consists of recurring headaches that come in clusters and cause pain behind the eye so severe that they are also known as “suicide headaches.” The intense pain leads many sufferers to contemplate suicide, and some of them carry it out. Worldwide, about 4 million people suffer from this condition in any given year.

Conventional medicine cannot offer adequate relief for cluster headache sufferers, but a growing body of evidence indicates that one to three doses of psilocybin or LSD can prevent attacks for months. Patients have reported anecdotally that vaporized DMT, another psychedelic drug, aborts attacks seconds after they begin.

The problem is that in almost every jurisdiction, psilocybin, LSD and DMT are prohibited substances. Psilocybin has a long history of ritual use by Indigenous peoples in Mexico and Central America. More recently, psilocybin and LSD have been used by millions of people for recreational as well as religious purposes.

Switzerland provides a model for reconciling the need for compassionate treatment with the need for legal barriers against the widespread use of drugs that should be taken under supervision. Since 2014, the Swiss Federal Office of Public Health has authorized medical practitioners to use prohibited substances as a last resort to treat patients who have exhausted other remedies.

In 2024, 723 patients were treated with MDMA, LSD or psilocybin. The majority of these treatments were for mental health conditions such as depression, anxiety and PTSD, but 16 patients were treated with either psilocybin or LSD for cluster headache or migraine. Nine cluster headache patients were treated at a single pain clinic in Zurich; a case series reported that eight showed temporary improvement, with the attacks ceasing in six.

Canada has a procedure for permitting the use of psilocybin to treat cluster headaches, but so far, it has been invoked for only one patient with that condition. Australia permits authorized psychiatrists to prescribe psychedelic substances, but only for patients suffering from depression or PTSD. In both these countries, there is a strong case for widening access.

Not surprisingly, when laws bar doctors from prescribing drugs that may spare their patients the agony of cluster headaches, some patients will buy the drugs on the street and take them at home. Even if these patients benefit, allowing doctors to prescribe the drugs is the only way to guarantee the purity of the drug and that it will be taken under adequate supervision. Moreover, every patient who self-medicates is a lost opportunity to increase our knowledge of how best to treat this excruciating condition.

Standard methods of assessing the importance of treating a medical condition include counting the number of years of life saved, adjusted for the quality of those years. Jonathan Leighton, founder of the Organization for the Prevention of Intense Suffering, suggested in his book “The Tango of Ethics: Intuition, Rationality and the Prevention of Suffering” that this has led to a neglect of conditions involving extreme pain. Leighton proposes the parallel use of specific metrics for severe and extreme suffering. Although we could, in theory, assign a strongly negative weighting to a year lived with frequent cluster headaches, to do so would imply that it could be an improvement if the person with the condition were to die. Health economists are, no surprise, reluctant to use a metric that does this.

A recent article in Nature: Humanities and Social Science Communications found the funding provided in the United Kingdom for research on cluster headaches to be “orders of magnitude” less than that provided for multiple sclerosis, a condition that affects a similar number of people. The authors conclude that, given that we regard the provision of anesthesia for surgery to be essential, we should also recognize relief for extreme pain as essential. Finding ways to do so should warrant the highest funding priority.

A new initiative called Clusterfree has launched global open letters calling on governments to provide legal access to psychedelics for people with cluster headaches. I have signed, and I hope that you will, too.

Peter Singer

Peter Singer is a professor in medical ethics at the Centre for Biomedical Ethics, National University of Singapore, and emeritus professor of bioethics at Princeton University. The views expressed here are the writer’s own. — Ed.

(Project Syndicate)