Abstract

Near-death experiences (NDEs) are complex subjective experiences, which have been previously associated with the psychedelic experience and more specifically with the experience induced by the potent serotonergic, N,N-Dimethyltryptamine (DMT). Potential similarities between both subjective states have been noted previously, including the subjective feeling of transcending one’s body and entering an alternative realm, perceiving and communicating with sentient ‘entities’ and themes related to death and dying. In this within-subjects placebo-controled study we aimed to test the similarities between the DMT state and NDEs, by administering DMT and placebo to 13 healthy participants, who then completed a validated and widely used measure of NDEs. Results revealed significant increases in phenomenological features associated with the NDE, following DMT administration compared to placebo. Also, we found significant relationships between the NDE scores and DMT-induced ego-dissolution and mystical-type experiences, as well as a significant association between NDE scores and baseline trait ‘absorption’ and delusional ideation measured at baseline. Furthermore, we found a significant overlap in nearly all of the NDE phenomenological features when comparing DMT-induced NDEs with a matched group of ‘actual’ NDE experiencers. These results reveal a striking similarity between these states that warrants further investigation.

Introduction

Near-death experiences (NDEs) are complex experiential episodes that occur in association with death or the perception that it is impending (Moody, 1975; Greyson, 1983). Prospective studies with cardiac arrest patients indicate that the incidence of NDEs vary between 2–18% depending on what criteria are used to determine them (Parnia et al., 2001; Van Lommel et al., 2001; Schwaninger et al., 2002; Greyson, 2003). Although there is no universally accepted definition of the NDE, common features include feelings of inner-peace, out-of-body experiences, traveling through a dark region or ‘void’ (commonly associated with a tunnel), visions of a bright light, entering into an unearthly ‘other realm’ and communicating with sentient ‘beings’ (Moody, 1975; Ring, 1980; Greyson, 1983; Martial et al., 2017). Reviewing the phenomenology of NDEs, we have been struck by similarities with the experience evoked by the classic serotonergic psychedelic N,N, Dimethyltryptamine (DMT) (Strassman et al., 1994; Strassman, 2001).

Commonly described features of the DMT experience include a feeling of transcending one’s body and entering into an alternative ‘realm’, an acoustic perception of a high pitched ‘whining/whirring’ sound during the onset of the experience, perceiving and communicating with ‘presences’ or ‘entities’, plus reflections on death, dying and the after-life (Sai-Halász et al., 1958; Strassman, 2001; Gouzoulis-Mayfrank et al., 2005). Furthermore, the reported vividness of both subjective experiences have led to NDE experiencers and DMT users describing the states they enter as ‘realer than real’ (for NDEs see Moody, 1975; Thonnard et al., 2013; for DMT see Strassman, 2001).

The term near-death exerpience (NDE) was coined by philosopher Raymond Moody more than 40 years ago (Moody, 1975). Remarkably, the overlap between the phenomenology of the classic serotonergic psychedelic experience and NDEs was highlighted by Moody himself more than 4 decades ago (Moody, 1975) and these similarities have formed the basis of a popular hypothesis on the pharmacology of NDEs, i.e., that endogenous DMT is released in significant concentrations during the dying process (Strassman, 2001), but see (Nichols, 2017) for a critique of this hypothesis. The psychological state produced by the DMT-containing Amazonian brew, ayahuasca (the literal translation of ‘ayahuasca’ from quechua is ‘the vine of the dead’ or ‘the vine of the soul’), has also been linked to themes of death and dying (Shanon, 2005) as have psychedelics in general (Millière, 2017), e.g., with the psychology of psychedelic-induced ‘ego-death’ being likened to that of actual death (Leary et al., 200.

Both the psychedelic experience and NDEs appear to be sensitive to contextual factors such as prior psychological traits and state (‘set’), the environment (‘setting’) in which the experience unfolds (Metzner et al., 1965; Studerus et al., 2012) – plus the broader cultural context in which they are embedded (Wallace, 1959; Hartogsohn, 2017; Carhart-Harris et al., 201. For example, controlled research has found that certain personality traits, e.g., ‘absorption’ and ‘neuroticism’ can predict the intensity and quality of a psychedelic experience (Studerus et al., 2012; Carhart-Harris et al., 2015, 2018; Carbonaro et al., 2016; Barrett et al., 2017) while readiness to ‘let go’ and quality of the environment also seems to be predictive of response (Carhart-Harris et al., 201. In a similar fashion, the prevalence and nature of NDEs appear to be sensitive to environmental, demographic and personality variables, such as etiology and prognosis of the NDE, age, absorption and a propensity to report paranormal experiences (Kohr, 1983; Greyson, 2003). Cultural factors are presumed to influence the psychedelic experience (Carhart-Harris et al., 201 and have been found to influence the content of NDEs, (Kellehear, 1993; Kellehear et al., 1994).

The near-death experience has been associated with long-term positive changes in psychological well-being and related outcomes; more specifically, greater concern for others, reductions in distress associated with the prospect of dying, increased appreciation for nature, reduced interest in social status and possessions, as well as increased self-worth have all been observed and/or described post NDEs (Noyes, 1980; Ring, 1980; Groth-Marnat and Summers, 199. Relatedly, recent results from studies with psychedelic compounds have shown similar long-term positive changes. For example, reduced death anxiety (Grob et al., 2011; Gasser et al., 2015; Griffiths et al., 2016; Ross et al., 2016), pro-ecological behavior (Forstmann and Sagioglou, 2017; Nour et al., 2017) and nature relatedness (Lyons and Carhart-Harris, 201, significant clinical improvements in depressed patients (Osório et al., 2015; Carhart-Harris et al., 2016; Palhano-Fontes et al., 201 and recovering addicts (Johnson et al., 2014; Bogenschutz et al., 2015; Bogenschutz and Johnson, 2016) and lasting improvements in psychological well-being in healthy populations (Griffiths et al., 2011; Carhart-Harris et al., 2017) have all been observed. Thus, overlap between near-death and psychedelic experiences may extend beyond the acute experience into longer-term psychological changes.

While the subjective effects of DMT have been researched in the past (Strassman et al., 1994; Gouzoulis-Mayfrank et al., 2005), they have tended to be collapsed into broad categories or dimensions of experience (e.g., visual, somatic and emotional effects) as determined by standard ‘altered states of consciousness’ rating scales (Strassman et al., 1994; Studerus et al., 2010). The degree to which DMT specifically induces near-death type experiences has never been directly measured, however.

This current within-subjects, placebo-controlled study aimed to directly measure the extent to which intravenous DMT given to healthy volunteers in a laboratory setting could induce a near-dear type experience as determined by a standard NDE rating scale (Greyson, 1983). Importantly, we also aimed to address how these experiences compared with a sample of individuals who claim to have had ‘actual’ near-death experiences. To our knowledge, this is the first time that the relationship between DMT experiences and (non-drug-induced) NDEs has ever been formally addressed.

We hypothesized that DMT would induce near-death type experiences of an equivalent intensity to those seen previously in the context of ‘actual’ NDEs, and to a significantly greater extent than in the placebo condition. Based on aforementioned work on NDEs, we also hypothesized that age, personality and a propensity toward delusional thinking would correlate with DMT-induced near-death experiences.

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Discussion

This study sought to examine the degree to which features commonly reported in NDEs are elicited by the potent serotonergic psychedelic DMT in a placebo-controlled study. Results revealed that all 13 participants scored above the standard threshold for an NDE in relation to their DMT experiences (Greyson, 1983) and 15 of the 16 NDE items were rated significantly higher under DMT compared to placebo, with 10 of these reaching statistical significance after multiple testing correction.

Especially strong overlap was seen between DMT-induced near-death type experiences and mystical-type experiences (MEQ, Griffiths et al., 2006, 2016; Kometer et al., 2015), with the Mystical factor of the MEQ (which contains items such as “sense of being at a spiritual height” and “experience of oneness or unity with objects and/or persons in your surroundings”) showing the highest relationship with NDE total scores. Intriguingly, DMT-induced NDE scores were significantly correlated with baseline-measured delusional thinking. Perhaps most interesting of all however, when these DMT data were compared with those from a matched sample of ‘actual’ NDEs, a comparable profile was evident, with few discernable differences between the experiences of the actual NDE cases and those induced by DMT. Taken together, these results reveal a striking similarity between the phenomenology of NDEs and experiences induced by the classic serotonergic psychedelic, DMT.

As reported above, 10 of 16 NDE items were scored significantly higher under DMT than placebo. Items that did not survive multiple comparison correction (experiences of extrasensory perception, life-review, precognition of future events, increased speed of thoughts and seeing deceased people/relatives) are also items that are less commonly endorsed in ‘actual’ NDEs (Schwaninger et al., 2002; Greyson, 2003; Vanhaudenhuyse et al., 2009). The Affective subscale of the NDE scale was scored particularly highly under DMT, and emotion is also a prominent feature of actual NDEs (Greyson, 1983, 2003; Schwaninger et al., 2002; Martial et al., 2017). Subtle differences that were apparent between the DMT condition and NDEs (e.g., the experience of entering an unearthly realm was enhanced for DMT vs. actual NDEs, whereas coming to a point of no return was scored higher in actual NDEs compared with the DMT experience) may be explainable by the very different contexts in which these experiences occur (e.g., DMT was given here with prior screening, psychological preparation and consent in a safe laboratory setting vs. an NDE occuring during an illness or unexpected accident) as much as differences due to the inducers themselves or their associated neurobiologies.

It is important to acknowledge that the phenomenology of NDEs is still a matter of some investigation. Initially, 15 NDE features were proposed when the term was first coined – based on interviews with more than 50 NDE ‘experiencers’ (Moody, 1975); after this, 5 core features were identified via structured interviews (Ring, 1980), and subsequently Greyson (1983) identified 16 features using statistical methods in a study comprising 73 different NDEs.

It has recently been shown that the temporal sequence of events unfolding during an NDE is highly variable between people and no prototypical sequence was identifiable in a sample of 154 participants, although four main dimensions were relatively consistent, namely: ‘out-of-body experiences,’ ‘seeing a bright light,’ ‘encountering spirits/people,’ and a ‘feeling of peace’ (Martial et al., 2017). The potential heterogeneity of NDEs cautions us to consider how intra and inter-individual variables, cultural characteristics and the environmental and psychological context in which they take place may influence the content of experiences as well as whether and how they are reported.

Personality has previously been associated with response to psychedelics (Studerus et al., 2012; Hartogsohn, 2016; Barrett et al., 2017). For example, trait ‘absorption’ has been shown to be predictive of sensitivity to psychedelics (Studerus et al., 2012), and the same has also been shown in relation to the intensity of ‘actual’ NDEs (Twemlow and Gabbard, 1984). Absorption has been linked to a serotonin 2A receptor polymorphism associated with greater signaling (Ott et al., 2005); thus, it is intriguing to consider whether abnormal serotonergic functioning may contribute to both psychedelic and NDEs (Carhart-Harris and Nutt, 2017). Here, we saw a trend toward absorption predicting DMT-induced NDE but this relationship did not quite reach statistical significance, perhaps due to insufficient statistical power or that the use of different doses might have masked this effect.

It has been previously shown that the reported intensity of NDEs is associated with a tendency to report so-called ‘paranormal’ experiences (Kohr, 1983; Greyson, 2003). Our results show that baseline delusional thinking (as measured by Peters’ Delusion Inventory), was strongly associated with NDE scores. One possible interpretation of this is that – like people with paranormal beliefs – people with higher than average delusional thinking are more emphatic in their endorsement of NDE phenomena as they view it as less at odds with their pre-existing belief systems and perhaps even see it as ‘evidence’ for metaphysical and/or mystical beliefs which they already endorse. Recent findings (Martial et al., 201 have found a strong relationship between ‘fantasy proneness’ and NDE phenomena reported by individuals in situations in which there has been no genuine threat to their lives (e.g., in meditative states or under intense psychological distress). These results support the view that individuals’ traits and beliefs might strongly influence the appearance of such phenomena in a range of different contexts, which could account for our current findings.

Relatedly, we found a strong relationship between scores of DMT-induced near-death type and mystical-type experiences. More specifically, we found a strong association between the total NDE score and the MEQ factors ‘Mystical’ and ‘Transcendence of Time and Space.’ The Mystical factor corresponds to items pertaining to an experience of unity or continuity between self/ego and the external world (known elsewhere as ‘dissolved ego-boundaries’- Nour et al., 2016), an intuitive feeling of so-called ‘sacredness’, and the experience of gaining insights into ‘ultimate truths’. The factor Transcendence of Time and Space corresponds to experiences of loss of one’s usual spatial and temporal orientation and a sense of vastness, continuity and eternity (Pahnke and Richards, 1970; Maclean et al., 2013). The strong overlap between these facets of mystical-type and NDEs may be due to similar items featuring in both scales (e.g., items pertaining changes in time perception, experiences of unity, feelings of peace) which could be seen as evidence of their strong phenomenological overlap – but there are also some items that are distinct between the scales, e.g., feelings of being separated from one’s one body, encountering beings or presences.

Recent work has consistently shown that the occurrence of mystical-type experiences is predictive of long-term therapeutic benefit from psychedelics (Maclean et al., 2011; Garcia-Romeu et al., 2014; Griffiths et al., 2016; Carhart-Harris et al., 2017, 2018; Roseman et al., 201 and similar mechanisms may be at play in relation to improved mental well-being post NDE (Moody, 1975; Noyes, 1980; Ring, 1980; Groth-Marnat and Summers, 199. It is pertinent to ask therefore, what common features shared between these states may be responsible for mediating the apparent long-term psychological benefits that follow them. Evidence suggests that that the experience of unity – which some have claimed is an inevitable counterpart to ego-dissolution (Nour et al., 2016) – may be the core component binding them both. The so-called ‘unitive experience’ was originally identified as the core component of the mystical experience by its most influential scholar, Walter Stace (Stace, 1960) and it is also recognized in descriptions of the ‘peak experience’ – an overtly secular equivalent of the so-called ‘mystical experience’ introduced by Maslow (1959), as well as the ‘oceanic feeling’ coined by Romain Rolland in conversation with Sigmund Freud, who believed the feeling to be regressive, recapitulating the state of consciousness inhabited by infants prior to the development of the ego (Freud, 1920). It is possible that complete ego-dissolution and the parallel unitive experience that accompanies it may be the common factor that can bridge between these different states and is also responsible for the longer-term psychological benefits associated with them. Another recent thought, is that a return of the brain to ‘criticality’ (Atasoy et al., 2017), albeit temporarily, may offer a reminder of one’s closeness with nature (Carhart-Harris, 201 and so what is left afterwards is as much an epistemic ‘reminder’ as anything else.

Detailed interviewing techniques could serve to improve our characterization of the phenomenology of both the DMT and NDE states (Petitmengin, 2006; Petitmengin and Lachaux, 2013), and future studies of the psychedelic state could benefit from adopting a more dynamic sampling approach, i.e., by attempting to detail the temporal unfolding of the experience – as has been done recently in the context of NDEs (Martial et al., 2017) and elsewhere in relation to stream of consciousness (Smallwood and Schooler, 2015). We predict that improved ‘capture’ of certain transient experiences within a broader psychedelic experience may help finesse our understanding of its psychology and associated neurobiology.

Rudimentary neurobiological models of the NDE have existed for almost 30 years, and have tended to lay emphasis on abnormal serotonergic and medial temporal lobe activity (Morse et al., 1989; Saavedra-Aguilar and Gómez-Jeria, 1989; Britton and Bootzin, 2004) – consistent with the predominantly serotonergic pharmacology of classic psychedelics (Nichols, 2016) as well as findings from fMRI (Tagliazucchi et al., 2014; Carhart-harris et al., 2016) and depth EEG recordings of human brain activity under psychedelics which implicate the medial temporal lobes (Carhart-Harris, 2007; Carhart-Harris and Nutt, 2014). Given strong associations between the temporal lobes and more specifically, medial temporal lobe structures, and unusual psychological experiences such as those featuring within NDEs (Carhart-Harris, 2007), we predict that the medial temporal regions may be implicated in some of the content and emotion-rich epochs that arise within the psychedelic state, such as complex imagery, entity encounters, and vivid autobiographical recollections. The relinquishment of top-down cortical control over temporal lobe activity may be an important component of this mechanism (Alonso et al., 2015; Kaelen et al., 2016; Timmermann et al., 2017).

Limitations

It is important to acknowledge this study’s limitations. The dose of DMT was not uniform for all participants due to this study being part of a dose-finding pre-study ahead of a larger EEG-fMRI study with DMT. The lower doses of DMT may have actually depreciated the true strength of the similarities between the DMT state and the near-death experience therefore, and we should also acknowledge that individuals included within the ‘actual’ NDE sample had to give NDE-scale scores above a specific threshold, whereas this pre-requisite wasn’t stipulated for our DMT sample.

Another limitation is that we cannot discount the influence of order effects as placebo sessions were always performed first (to avoid carryover and promote comfort for the DMT session) and thus, exposure to the NDE scale post placebo may have primed participants to experience NDE-like phenomena ahead of their DMT sessions – although this seems unlikely given the volume of other measures and time between sessions. The positive scores on the NDE scale might also reflect a general tendency to endorse ‘anything unusual’ in relation to the psychedelic experience, particularly as psychedelics have been shown to promote suggestibility (Carhart-Harris et al., 2015). Contradicting this explanation, however: (1) participants’ mental state had largely returned to baseline by the time they completed the NDE scale, (2) responses to the different dimensions of the NDE scale resembled those seen in relation to actual NDEs, and (3) an open interview performed post experience (but before questionnaires were completed) promoted careful reflection on the details of the DMT state. That one participant scored on the threshold for an NDE in the placebo session suggests that the NDE scale may have a somewhat liberal threshold for determining NDEs – and thus may warrant revision.

As both psychedelics and the NDE phenomena appear to be strongly influenced by contextual factors (Kellehear et al., 1994; Carhart-Harris et al., 201, it could be argued that significant differences may exist regarding phenomenological features between both experiences. Nonetheless, considering the strong overlap on the items of the NDE scale, the study of such differences might require the use of other methods addressing nuances not explored here (e.g., the use of questionnaires addressing contextual factors and qualitative studies).

We should also consider that although the study of the phenomenology of NDEs and psychedelic experiences may inform on each other in a reciprocal way, using one psychological phenomenon to model another, particularly if they are as abstract as the near-death and psychedelic experiences are, these may be fraught with problems (see Langlitz, 2017 for a detailed reflection on psychedelics as models of other mental and psychiatric phenomena). For this reason, better understanding their (presumed) shared neurobiology may provide the necessary bedrock to ground the science of these fascinating states.

Conclusion

This study aimed to examine potential overlap between the phenomenology of NDEs and those associated with the potent serotonergic psychedelic DMT. Results revealed an intriguingly strong overlap between specific and broad features of these states, with DMT participants scoring high on a standard measure of NDEs and in a comparable way to people reporting bona fide NDEs, with only subtle differences that might relate more to obvious contextual differences than anything to do with the specific inducers themselves.

Indeed, these present results suggest that certain contextual factors (e.g., delusional thinking and personality trait absorption) can significantly mediate both the intensity and quality of the DMT-induced NDE-like experiences, advancing the notion that – as with the psychedelic experience more broadly (Carhart-Harris et al., 201 – the intensity and content of NDEs are context-dependent. This study’s findings warrant further investigation to address the putatively strong overlap between the phenomenology and neurobiology of DMT (and other psychedelic) experiences and ‘actual’ near-death experiences, particular given some of the scientifically problematic yet influential claims that have been made about NDEs (Alexander, 2012).

Better understanding of both the psychology and neurobiology of dying (Borjigin et al., 2013) – e.g., by using psychedelics to model it – may have implications for how we view this most inevitable and universal phenomenon, potentially promoting a greater familiarity with and healthy acceptance of it.

Why taking ayahuasca is like having a near-death experience

A man being handed ayahuasca
Ayahuasca contains the psychedelic drug DMT

Brian Van Tighem / Alamy Stock Photo

By Sam Wong

A psychedelic drug taken as part of the South American plant brew ayahuasca produces effects that are strikingly similar to near-death experiences, a study has found.

That means that feelings of leaving the body or inner peace associated with life-threatening experiences may simply be explained by changes in how the brain works, and aren’t evidence of paranormal phenomena, say the researchers.

DMT is the main psychoactive ingredient in ayahuasca, which is used as a sacrament by some indigenous peoples in the Amazon. People who take it commonly describe feeling that they transcend their body and enter another realm.

Chris Timmermann and colleagues at Imperial College London gave DMT intravenously to 13 volunteers and asked them to fill in a questionnaire used to assess near-death experiences. In an earlier session, the same volunteers were given an intravenous placebo, and they did not know which session would involve the real drug.
Join us at New Scientist Live: Where Chris Timmermann will explain how DMT can help us explore the mechanisms of consciousness

After the DMT session, all 13 participants got results on the questionnaire that met the criteria for a near-death experience. In particular, they reported feeling as though they entered an “unearthly environment”, feeling “incredible peace or pleasantness”, having heightened senses and a feeling of unity with the universe.

When their responses were compared with responses from a set of 13 people who had reported actual near-death experiences, there were no statistically significant differences between the groups.
Dissolving the ego

Little is known about what happens in the brain when someone has a near-death experience. The subjective similarity with a DMT trip suggests that psychedelics could shed some light on the phenomenon, says Timmermann.

Psychedelic drugs such as DMT work mainly by affecting the serotonin system in the brain. Although this study didn’t measure brain activity, “we could speculate that something similar is going on during near-death experiences,” says Timmermann.

The feeling of leaving the body or living through death might be linked to the phenomenon of ego dissolution, a loss of one’s sense of self which is a common feature of the psychedelic experience. Brain imaging studies show that the default mode network, a collection of brain regions linked to our sense of self, becomes less cohesive under the influence of other psychedelic drugs, and this may explain why some people feel that they have survived the death of their ego.

Intriguingly, DMT appears in trace amounts in blood and urine, but a source for the molecule inside the body has not been identified. Some have hypothesised that it is produced in the brain when we are facing death, but this is highly speculative.

Near-death experiences are sometimes said to give people a different outlook on life, and may be helpful in reducing fear of death and increasing people’s concern for others. Similar effects have been reported for psychedelic experiences, and a number of studies have reported positive effects on wellbeing when patients with life-threatening cancer take the drug psilocybin.