After spending decades in the graveyard of hippie culture, psychedelics are making a comeback. The “psychedelic renaissance” has slowly been building pace, finally breaking through our collective consciousness with the publication of Mr Michael Pollan’s How To Change Your Mind in May of last year, and achieving peak zeitgeist this spring when Ms Gwyneth Paltrow suggested that psychedelics might just be the next big thing in wellness.

Mr Pollan explores the therapeutic aspects of LSD and psilocybin (the “magic” in magic mushrooms) as well as the “applied mysticism” of the ritualistic use of plant-based psychedelics. He documents a movement driven by people who understand the life-changing potential of altered states, and who risk incarceration every time they assist someone on a journey into the recesses of their mind.

Dubbed the “spirit molecule” by Dr Rick Strassman, an associate professor of psychiatry at the University of New Mexico School of Medicine, dimethyltryptamine (DMT) – a tryptamine alkaloid that occurs naturally in some plants, such as ayahuasca – is at the heart of a potent brew concocted by the shamans of South America who believe it has the power to heal their community and provide a gateway to the spirit world.

Five years ago, few people had heard of ayahuasca. Today, there are ceremonies everywhere from London to Los Angeles. Thousands of Westerners land in Iquitos in Peru, to get their fill of the ancient tea, fueling a highly profitable – and unregulated – industry that is now on the brink of collapse. What was once the reserve of hardcore spiritual seekers is now mainstream. According to Mr Carlos Suárez Álvarez, creator of Ayahuasca, Iquitos And Monster Vorāx, a series of multimedia books that aims to illustrate the ayahuasca phenomenon, 10 of the 40 biggest camps reap nearly £5m annually, hosting foreigners for more than £1,000 per stay.

There are several reasons psychedelics have become popular once more. In an era where antidepressant use is widespread and a cocktail of work, smartphones and social media is upping the global stress quotient, proponents suggest that psychedelics could present a paradigm shift in psychotherapy and healthcare. The academic community is starting to echo what a handful of pioneering doctors have been saying for decades: that the psychedelic experience has the potential to rewire our brains, helping to alleviate symptoms of anxiety, depression and post-traumatic stress disorder.

Much of the research began in the 1950s when researchers in Saskatchewan began treating alcoholics with lysergic acid diethylamide (aka LSD). The use of psychedelics as a curative for compulsive behaviour and mental disorders grew from there. A range of psychedelics were administered by pioneering psychiatrist, Dr Humphry Osmond, to those struggling with depression, schizophrenia and autism. LSD, which had been discovered by scientist Mr Albert Hofmann, was even administered in group psychotherapy in prisons. There was a suggestion that the experience psychedelics offered could change the way a person lived life; the clinical evidence, however, was scant and riddled with holes.

By the 1960s, psychedelics had, infamously, become a central component of the counter-culture. Their popularity grew so quickly that, in 1970, research was stopped dead in its tracks by the Controlled Substances Act in the US.

But, after a decades-long hiatus, new research is bringing the use of psychdelics to fore. A 2018 study from the University of California concluded that psychedelics can alter the malfunctioning circuitry associated with mood and anxiety disorders by changing the very structure of neurons. Brain imaging studies conducted by the Beckley Foundation and Imperial College London have shown that LSD decreases communication in the regions of the brain that control and repress consciousness, allowing participants to experience “ego dissolution”.

Put simply, LSD could disorganise cortical function to the point where disparate parts of the brain can communicate freely. “Normally, our brain consists of independent networks that perform separate specialised functions, such as vision, movement and hearing, as well as more complex things like attention,” says Dr Robin Carhart-Harris of Imperial College, who led the research. “However, under LSD, the separateness of these networks breaks down and instead you see a more integrated or unified brain.”

In March of this year, the US Food and Drug Administration approved a ketamine-based nasal spray from Johnson & Johnson to treat depression (use enough ketamine and it will flood the right receptors to alleviate mood and rewire the brain; use too much and it’s essentially a tranquilliser). Meanwhile in Europe, technology investors raised a staggering $43m in financing for a psychedelic biotech company called ATAI. Institutions such as New York University are administering psilocybin to cancer patients in an effort to help them deal with the proximity of death and, in Silicon Valley, micro-dosing is as common as popping a multivitamin. In fact, the idea of supplementing one’s diet with non-psychoactive doses of LSD, MDMA, mescaline or psilocybin is spreading quickly; between 10 and 20 micrograms a day are said to boost cognitive ability, focus and productivity – all without tripping off your nut.

But, of all the psychedelic experiences available to us, ayahuasca is inextricably linked with spirituality. Anecdotal evidence from believers of all ilks suggest that the plants in the drink are sentient and impart specific information. Practitioners may tell you that they left their body and travelled to other dimensions, or that they had visitations from spirits. This is the stuff that, in many cases, creates long-lasting personal transformation but leaves scientists nonplussed or scratching their heads.

To that end, it’s worth making the distinction between the terms “hallucinogen” and “entheogen”: the latter is defined a spiritual experience as opposed to a “trip” or a fabrication of the mind. Viewing psychedelics through this lens makes clinical research tricky, if not impossible. While scientists have a growing appreciation of how psychedelics work in the brain, they are yet to crack the neurobiology of the mystical encounters that occur so often during these altered states. And, perhaps that mystery is part of their beauty and, indeed, their allure.