Letter to the Editor

Abstract

Near-death experiences (NDE) have been scientifically described as an extraordinary experience after a life-threatening crisis (for example a cardio-pulmonary arrest) [[1]Thonnard M. Charland-Verville V. Brédart S. et al.Characteristics of near-death experiences memories as compared to real and imagined events memories.PLoS One. 2013; 8: e57620Crossref PubMed Scopus (48) Google Scholar]: “profound psychological events with transcendental and mystical elements, typically occurring to individuals close to death or in situation of intense physical or emotional danger” [[2]Greyson B. Near-death experience.Varieties of anomalous experiences. Examining the scientific evidence. American Psychological Association, Washington DC2000: 315-352Crossref Google Scholar].Due to the extremely subjective nature and the absence of any frame or reference, such an experience leads to various descriptions influenced by individual, cultural and religious factors: awareness of being dead, positive emotions, out of body experience, moving through a tunnel often communicating with an intense light, observation of colours, observation of a celestial landscape, meeting with deceased relatives or religious figures, flashbacks and life review, visualization of a border between life and death, etc [[3]van Lommel P. van Wees R. Meyers V. Elfferich I. Near-death experience in survivors of cardiac arrest: a prospective study in the Netherlands.Lancet. 2001; 358: 2039-2045Abstract Full Text Full Text PDF PubMed Scopus (326) Google Scholar]. NDE states can occur outside of any real imminence of death. In 2008, neuro-imaging studies demonstrated the important role of the temporo-parietal cortex, a region involved in the integration of multi-sensory information and self-awareness in the emergence of NDE [[4]Thonnard M. Schnakers C. Boly M. et al.Near-death experiences: fact and fancy.Rev Med Liege. 2008; 63: 438-444PubMed Google Scholar]. Functional cerebral imaging confirmed the important role of the temporo-parietal junction even if the visual information reported by the people has not yet been verified. Many theories on the origin of NDE have been proposed [[1]Thonnard M. Charland-Verville V. Brédart S. et al.Characteristics of near-death experiences memories as compared to real and imagined events memories.PLoS One. 2013; 8: e57620Crossref PubMed Scopus (48) Google Scholar]. They can be divided into several categories: the first refers to spiritual and transcendental approaches, the second to purely psychological approaches, and the latter to neurological or organic approaches. For our part, we propose a fourth one with a neuroendocrine theory. Indeed, our hypothesis is that there may be an endogenous release of endo-hallucinogenic substances in humans at the time of physiological stress and/or physical trauma, causing a NDE. That is to say, NDE would not be a passive phenomenon such as a physiological reaction linked to a decrease in vascular flow with cortical or deep cerebral pain [[2]Greyson B. Near-death experience.Varieties of anomalous experiences. Examining the scientific evidence. American Psychological Association, Washington DC2000: 315-352Crossref Google Scholar], but rather an active secretive phenomenon with direct cortical response (for example at the level of the temporo-parietal junction). In the following table (Table 1), a list of hallucinogenic substances can be produced which could be the cause of manifestations comparable to NDE.Table 1List of putative hallucinogen substances related to « endogenous NDE ».KetaminLSDEcstasy/MDMAPsilocybine/psylocineAyahuascaIbotenic acid/muscimole (Amanita muscaria)Mescaline (peyotl)Salvinorin A (Salvia divinorium)Atropine (Atropa belladonna)Hyoscyamine (Datura, Jusquiame, mandragore)ScopolamineTHCTetrodotoxin Open table in a new tab This theory is not fortuitous, and is strengthened by medical anthropology knowledge and experience [5Eliade M. Le chamanisme et les techniques archaïques d’extase. Payot, Paris1951Google Scholar, 6Vallet O. Lafitte S. Laugrand F. Le chamanisme. Albin Michel, Paris2013Google Scholar, 7Clottes J. Lewis-Williams D. Les chamanes de la préhistoire.Transe et magie dans les grottes ornées. Seuil, Paris1996Google Scholar, 8Charlier P. Zombies: an anthropological investigation of the living dead. University of Florida, Miami2017Google Scholar]: throughout the world and at all times, mystical or religious visionaries have exploited different ways of altering their consciousness to reach a state of ecstasy. The multiplication of anthropological observations of shamanic practices shows the great variety of substances used to reach modified levels of consciousness, characterized by the feeling of leaving the body, a sensation of travel, vortex, extremely pleasant sounds and sensations, etc. The substances incriminated are the same as those previously mentioned (Table 1) and suggested in our theory. These experiences can be assimilated (or at least linked) to NDE, and can shed more light to our topic of interest. Further experiences are necessary to confirm or infirm whether neurotransmitters with endo-hallucinogenic effects secreted at times of physiologic stress produce comparable visions and sensations subjectively reported as a near-death experience.