By Christian Jarrett

First-hand accounts of what it is like to come close to death often contain the same recurring themes, such as the sense of leaving the body, a review of one’s life, tunnelled vision and a magical sense of reality. Mystics, optimists and people of religious faith interpret this as evidence of an after life. Sceptically minded neuroscientists and psychologists think there may be a more terrestrial neurochemical explanation – that the profound and magical near death experience is caused by the natural release of brain chemicals at or near the end of life.

Supporting this, observers have noted the striking similarities between first-hand accounts of near-death experiences and the psychedelic experiences described by people who have taken mind-altering drugs.

“I had the feeling of floating, still tied to the remains of my heavy body, but floating nonetheless. I rocked and moved, at times as if on a liquid, undulating surface, at other times rising upwards, like a helium-filled flat container.” Excerpt from Amazing First-time Experience in the K-hole, published by Phaeton at the Erowid Experience vaults.

Perhaps, near death, the brain naturally releases the same psychoactive substances as used by drug takers, or substances that act on the same brain receptors as the drugs. It’s also notable that psychedelic drugs have been taken by the shamans of traditional far-flung cultures through history as a way to, as they see it, visit the after world or speak to the dead.

To date, however, much of the evidence comparing near death experiences and psychedelic trips has been anecdotal or it’s been based on questionnaire measures that arguably struggle to capture the complexity of these life-changing experiences. Pursuing this line of enquiry with a new approach, an international team of researchers led by Charlotte Martial at the University Hospital of Liège has conducted a deep lexical analysis, comparing 625 written narrative accounts of near death experiences with more than 15,000 written narrative accounts of experiences taking psychoactive drugs (sourced from the Erowid Experience vaults), including 165 different substances in 10 drug classes.

The analysis, published in Consciousness and Cognition, uncovered remarkable similarities between the psychological effects of certain drugs – most of all ketamine, but also notably the serotonergic psychedelic drugs like LSD – and near death experiences. Indeed, the five most common category terms in the narrative accounts of people who’d taken ketamine were the same as the five most common in the near death experience accounts suggesting “shared phenomenological features associated with an altered state of perception of the self and the environment, and a departure from the everyday contents of conscious mentation”:

“perception (“face“, “vision“, “saw“), emotion (“fear“), consciousness and cognition (“reality“, “moment“, “universe“, “understand“, “consciousness“, “memory“, “explain“, “learn“), the self and others (“own“, “arm“, “self“, “person“, “human“, “everyone“, “others“) and setting (“door“, “floor“, “inside“, “outside“).”

The findings back up the observations of some of the most famous twentieth-century explorers of the psychedelic world – US psychologist Timothy Leary described trips as “experiments in voluntary death” and the British-born writer and philosopher Gerald Heard said of the psychedelic experience, “that’s what death is going to be like. And, oh, what fun it will be!”.

To an extent the results also support neurochemical accounts of near death experience and especially the controversial proposal that such experiences are caused by the natural release of an as-yet-to-be-discovered ketamine-like drug in the brain (adding plausibility to this account, ketamine is known to act on neural receptors that when activated help to prevent cell death and offer protection from lack of oxygen).

As the researchers note wryly, “unlike other human experiences, dying is difficult to study under controlled laboratory conditions by means of repeated measurements” making it a challenge to investigate near-death experiences experimentally. Although the new research lacks laboratory control, on the plus side the lexical comparison Martial’s team conducted is “massive both in terms of the investigated drugs and the number of associated reports”.

The limitations of the current approach, including a reliance on retrospective reports, often decades old, means, as the researchers put it, that they cannot validate nor refute the neurochemical models of near death experiences. “However,” they add, “our results do provide evidence that ketamine, as well as other psychoactive substances, result in a state phenomenologically similar to that of ‘dying’ … This could have important implications for the pharmaceutical induction of near death experience-like states for scientific purposes, as well as for therapeutic uses in the terminally ill as a means to alleviate death anxiety.”

—Neurochemical models of near-death experiences: A large-scale study based on the semantic similarity of written reports

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest