One of the more compelling areas of research currently being investigated in the world of psychedelic science is psilocybin-assisted psychotherapy to improve emotional well-being in patients with life-threatening cancer. A new study is offering the first long-term insights into the efficacy of the treatment, revealing a single dose of psilocybin, in conjunction with psychotherapy, is still offering persistently positive effects up to five years later.

Dealing with the profound existential distress of a life-threatening cancer diagnosis is a major challenge for most patients. As many as 40 percent of cancer patients are known to develop clinically significant signs of depression or anxiety, and these mental health issues have been linked to worse treatment outcomes or, in some instances, suicide.

Some of the earliest psychedelic studies in the 1950s and 60s explored the effects of LSD on depression and anxiety in cancer patients before research in the area froze for several decades due to societal prohibitions. But post-2000 saw a thawing of regulations, and some of the most comprehensive trials to date have been investigating the potential for psychedelics in treating patients with life-threatening illness suffering existential distress.

The acute results from these studies have been incredibly promising but so far there has been little investigation into the long-term efficacy of these psychedelic interventions. In terms of psychedelic psychotherapy for patients with life-threatening illnesses, the longest follow-up study to date has been 12 months.

A newly published study in the Journal of Pharmacology is offering some of the best long-term insights into psychedelic psychotherapy to date. The study follows a previously published investigation into a single moderate dose of psilocybin, in conjunction with psychotherapy, for patients with cancer-related existential distress.

The 2016 double-blind, placebo-controlled, crossover study recruited 29 patients. By the six-and-a-half-month follow-up point, between 60 and 80 percent of the patients displayed clinically significant improvements in depression and anxiety symptoms.

The new study reports on two further long-term follow-up points investigating whether the effects of the psilocybin-assisted psychotherapy persisted for several years. Only 16 of the original 29 patients were still alive for the follow-up study, one of whom declined to participate and a second who died before the final follow-up date. This left 14 subjects to evaluate with an average final follow-up of four and a half years.

The long-term results were strikingly positive, recalling similar efficacy to the originally published study. Between 60 and 80 percent of the remaining subjects still fitted the criteria for clinically significant anxiolytic or antidepressant responses and the vast majority of the subjects ranked the single psilocybin treatment as one of the most meaningful and spiritually significant experiences of their lives.

It may be fair to suggest that it is unsurprising the long-term effects are so positive considering around 70 percent of the surviving cohort were in partial, or complete, remission at the final long-term follow-up point. However, the persistent meaningful experiences reported by the cohort in relation to the single psilocybin dose suggests long-term positive psychological effects can be attributed to the treatment.

So, not only does it seem the psychedelic-assisted psychotherapy helps patients move through the acute months following a major cancer diagnosis, but the experience may be aiding the surviving patients in positively contextualizing the traumatic experience years later.

“There’s a reckoning, which came with cancer, and this reckoning was enhanced by the psilocybin experience,” writes one of the patients five years later as part of the long-term follow-up questionnaire. “I have a greater appreciation and sense of gratitude for being alive.”

Another patient quoted in the new study offers a compelling sense that the psychedelic experience fundamentally changed their approach to the world. Again, this impression was nearly five years after the single psilocybin treatment.

“The psilocybin experience changed my thoughts about myself in the world. I see myself in a less limited way. I am more open to life. It has taken me out from under a big load of feelings and past issues in my life that I was carrying around.”

Gabby Agin-Liebes, lead author on the new study and co-author on the original 2016 study, keenly notes that these positive results seem to be due to the larger treatment regime of nine psychotherapy sessions in conjunction with the single psilocybin dose. Agin-Liebes does not believe these positive results can occur from a single psychedelic experience divorced from the broader treatment method and suggests the controlled therapeutic process is vital to the efficacy of this kind of psychedelic treatment.

“Psychedelic experiences are uniquely influenced by context in which they occur,” Agin-Liebes tells New Atlas in an email. “The importance of context can not be overemphasized. Psychedelics are different from other psychiatric medications in that their benefits seem to be very dependent upon the context in which they are ingested. In more traditional medications (e.g., antidepressants), the persistent presence of the drug in the body affects biological process, which lead to psychological and behavioral effects independent of the contexts in which medication is taken.”

Exactly how a single dose of psilocybin, in conjunction with psychotherapy, confers such profound and enduring effects up to five years later is still unclear. Agin-Liebes points to a recent paper from Imperial College London's Robin Carhart-Harris and Karl Friston as the most compelling holistic exploration of the mechanisms underpinning these persistent positive effects.

“The most compelling and scientifically grounded theory relates to psilocybin's potential for inducing a flexible brain state, particularly people who experience more rigid brain states,” explains Agin-Liebes. “Psychedelics appear to relax the brain's biased patterns of information processing and beliefs and allow for more "bottom-up" information to enter into one's consciousness.”

A number of larger clinical trials are currently ongoing, exploring the potential for psilocybin-assisted psychotherapy to address major depression and various addiction issues, as well as further validating the treatment for existential distress related to life-threatening illness.

The new study was published in the Journal of Psychopharmacology.