Near-death experience

A near-death experience (NDE) is a profound personal experience associated with death or impending death, which researchers describe as having similar characteristics. When positive, which most, but not all reported experiences are,^[1] such experiences may encompass a variety of sensations including detachment from the body, feelings of levitation, total serenity, security, warmth, joy, the experience of absolute dissolution, review of major life events, the presence of a light, and seeing dead relatives. While there are common elements, people's experiences and their interpretations of these experiences generally reflect their cultural, philosophical, or religious beliefs.^[2][3]

NDEs usually occur during reversible clinical death. Explanations for NDEs vary from scientific to religious. Neuroscience research hypothesizes that an NDE is a subjectivephenomenon resulting from "disturbed bodily multisensory integration" that occurs during life-threatening events.^[4] Some transcendental and religious beliefs about an afterlife include descriptions similar to NDEs.^{[5][6][7][8][9]}

The equivalent French term expérience de mort imminente ("experience of imminent death") was proposed by French psychologist and epistemologist Victor Egger as a result of discussions in the 1890s among philosophers and psychologists concerning climbers' stories of the panoramic life review during falls.^[10][11] In 1892, a series of subjective observations by workers falling from scaffolds, soldiers who suffered injuries, climbers who had fallen from heights and other individuals who had come close to death such as in near drownings and accidents was reported by Albert Heim. This was also the first time the phenomenon was described as a clinical syndrome.^[12]

In 1968, Celia Green published an analysis of 400 first-hand accounts of out-of-body experiences.^[13] This represented the first attempt to provide a taxonomy of such experiences, viewed simply as anomalous perceptual experiences or hallucinations. In 1969, Swiss-American psychiatrist and pioneer in near-death studies Elisabeth Kübler-Ross published her well-known book On Death and Dying: What the Dying Have to Teach Doctors, Nurses, Clergy, and Their Own Families.^[14] The term "near-death experience" was used by John C. Lilly in 1972.^[15] The term was popularized in 1975 by the work of psychiatrist Raymond Moody, who used it as an umbrella term for out-of-body experiences (OBEs), the "panoramic life review", the Light, the tunnel, or the border.^[12]

A 1975 study conducted by psychiatrist Raymond Moody on around 150 patients who all claimed to have witnessed an NDE stated that such an experience has fifteen elements.^[16][17] Moody focused in depth on approximately 50 cases from the group.^[16] One of the unifying aspects of all these patients' experiences was that they had suffered from critical illness, experienced life-threatening conditions or died.^[16][17] Eleven of the fifteen elements pertain to the experience itself and include:

1. Finding it challenging to express the experience in one's own words.
2. Learning one is dead from spectators or doctors.
3. One's pain is replaced by pleasant sensations or/and feelings of peace.
4. Hearing a disturbing noise or pleasant unearthly music.
5. Travelling through a dark tunnel.
6. Finding oneself outside the body.
7. Meeting other people.
8. Meeting with a being of light.
9. Panoramic review of one's life.
10. Arriving at boundary, frontier or point of no return.
11. Returning to one's body and earthly life.

Moody then described four more elements that relate to events occurring after the experience:^[17]

1. Sharing the experience with other people.
2. Impact on one's life.
3. Changing one's view of death.
4. Corroboration of the experience.

Moody explained how not every NDE will have each and every one of these steps, and how it could be different for each experience.

Kenneth Ring (1980) simplificó las observaciones de Moody y subdividió la ECM en un continuo de cinco etapas (utilizando los 15 elementos de Moody como inspiración). Las subdivisiones fueron: ^{[ 18 ]}

1. Paz
2. separación corporal
3. Entrando en la oscuridad
4. Ver la luz
5. Entrando en otro reino de existencia, a través de la luz.

La etapa final es la persona que está siendo reanimada. ^{[ 19 ]}

Dado que las poblaciones de pacientes estudiadas desde la publicación original de Moody se han alejado de la definición original de ECM (y, por lo tanto, de los estados fisiopatológicos resultantes de enfermedades críticas, muerte o cercanía a la muerte), se ha vuelto difícil comparar publicaciones revisadas por pares donde los pacientes tienen diversas condiciones médicas y no médicas. ^{[ 17 ]} Las guías recientes han abordado el desafío proponiendo hacer una distinción clara entre los grupos de pacientes que han experimentado una experiencia cercana a la muerte auténtica, como en la publicación original de Moody, y otras experiencias (médicas y no médicas). ^{[ 17 ]} Para identificar mejor las poblaciones de pacientes, las guías enfatizan la importancia de estudiar a los pacientes cuyas experiencias siguen el arco narrativo de las experiencias trascendentales originales de Moody: ^{[ 17 ]}

1. Una relación con la muerte.
2. Una sensación de trascender el mundo físico o material.
3. Inefabilidad.
4. Cambios beneficiosos en la vida ligados a un sentido más profundo de significado y propósito.

Las directrices también recomiendan centrarse en experiencias en las que:

• La gravedad de la enfermedad conduce a la pérdida de conciencia (LOC); y
• No hay signos de los fenómenos habituales asociados al coma, como sueños típicos, delirio o pensamiento delirante, independientemente de si la persona estuvo en la UCI o en un entorno diferente.

Los dos últimos puntos son importantes:

• para identificar adecuadamente las experiencias relacionadas con la muerte;
• para excluir enfermedades críticas relacionadas con el coma/que ponen en peligro la vida; y
• para excluir diversas experiencias humanas no relacionadas con la muerte. ^{[ 17 ]}

Due to a poor definition of what being "near-death" means, over the years researchers have drifted away from studying the same populations as Moody where patients suffered from critical illness, cardiac arrest or were in life critical-conditions.^[17] For example, in one series, 22% of the mislabeled NDEs have been claimed to occur during general anesthesia.^[22] There is disagreement between the 2022 guidelines and another author about the existence of some common elements or not:^[17][23]

• Classical (or authentic) near-death experiences occurring in populations facing impending death or death; and
• mislabeled NDEs occurring in populations not facing impending death or death.

The 2022 guidelines^[17] stress that the themes of authentic death experiences have little in common with mislabeled NDEs, except perhaps for shallow similarities, like mentioning religious symbols or saying the experience felt peaceful. The physiological context of patients near-death or experiencing death (as defined by cardiopulmonary criteria) leads to a decline in mental clarity and consciousness and, in extreme cases, complete loss of detectable cerebral function.^[17] Paradoxically, genuine/authentic near death experiences—characterized by coherence, meaning, purpose, and lucid life review—arise during this state, not under normal conditions of preserved brain metabolism and function.^[17] According to the 2022 guidelines,^[17] experiences termed "NDE-like" including those induced by ketamine or DMT, reliably display features unlike recalled experiences of death:

• distorted body sensations,
• inflated or self-centered perspectives, and
• varied imagery such as elves, celebrities, geometric forms, aliens, or bright neon scenes.

Likewise, dreams and seizures exhibit unrelated, non-authentic NDE themes.^[17]

Another author^[23] instead claims that similar traits have been identified despite the differences among populations being studied and these include:

• 50% awareness of being dead.^[23]
• 56% a sense of peace, well-being, painlessness, bliss, euphoria and other positive emotions.^[23]
• 24% an out-of-body experience (OBE). An OBE may be part of an NDE and involves a perception of one's body from an outside position, sometimes observing medical professionals performing resuscitation efforts.^[7][24][23]
• 31% a "tunnel experience" or entering a darkness. A sense of moving up, or through, a passageway or staircase.^[7][24][23]
• 32% being reunited with deceased loved ones or seeing religious figures.^[24][23][25]

A person's interpretation of an NDE experience often corresponds with one's cultural, philosophical, or religious beliefs. For example, in the US, where 46% of the population believes in guardian angels, the Light will often be identified as angels or deceased loved ones (or will be unidentified), while Hindus will often identify them as messengers of the god of death.^[2][3] The cultural beliefs held by NDErs seem to dictate some of the phenomena experienced during the NDE, but more so affect the later interpretation thereof.^[2]

In the years following Moody's descriptions of classical near-death experiences, reports of unpleasant experiences where people felt persecuted, distressed or frightened began to appear in the literature and in the media. These NDEs were categorized as negative or "hellish" (NDEs).^[26][27] More recent research, indicates that these distressing experiences generally do not share the same narrative structure or thematic elements as classical NDEs, nor do they exhibit the same long-term transformative impact, transcendent characteristics and ineffability.^[17] In essence, negative NDEs appear to be fundamentally and phenomenologically distinct from classical NDEs. In fact, most of these accounts are better understood as mislabelings of ICU delirium and delusions—phenomena that are well documented in the literature, particularly in the context of toxic metabolic disturbances, withdrawal syndromes, and other conditions that can produce persecutory, frightening, or dream-like experiences in hospitalized and critically ill patients.^[17][28][29] The original misclassification of these experiences lacked specific criteria or a scientific basis, and no formal definition or consensus has ever been established. Nevertheless, the use of these terms has contributed to the propagation of the idea of negative or "hellish" death-related experiences in the media and beyond.^[17]

Those who attempt suicide and survive will sometimes report enduring intense emotional pain that feels, to them, like a torment of their own creation.^[30] These individuals often find themselves in a state that they perceive as a personal and self-created hell.^[30]

Para mejorar el diagnóstico de las ECM, Bruce Greyson creó un cuestionario para personas que las experimentan, compuesto por 80 características. El cuestionario estudia efectos, mecanismos, sensaciones y reacciones comunes. ^{[ 31 ]} En 1983, Greyson reemplazó ese cuestionario con una escala para que la usaran los investigadores. ^{[ 31 ]} Casi cuatro décadas después del desarrollo de la escala estandarizada de Greyson para las ECM, han salido a la luz varias limitaciones. En particular, muchos de los términos y preguntas utilizados (en la escala de Greyson) —interpretados literalmente por el público— carecen de la precisión necesaria para distinguir de forma fiable las verdaderas ECM de otros tipos de experiencias humanas. Por ejemplo, la escala de Greyson incluye términos vagos como "sensaciones corporales extrañas", "lugar sobrenatural", "sentimientos místicos", "alegría", "armonía", "placer" y "espíritus", que podrían aplicarse a una variedad de experiencias que no son ECM. El término "sobrenatural", por ejemplo, podría describir fácilmente cualquier cosa, desde un entorno vacacional impresionante hasta el estado alterado provocado por las drogas. Debido a que esta escala se desarrolló sin una definición clara de lo que significa estar "cerca de la muerte", no incluyó criterios que vincularan la experiencia con un evento real que pusiera en peligro la vida. Como resultado, usar la escala fuera de su contexto previsto puede generar falsos positivos. Por ejemplo, alguien que recuerda unas vacaciones tranquilas y reflexiona sobre la vida podría cumplir con varios de los criterios de la escala —como paz, armonía, un lugar sobrenatural y revisión de la vida— lo que llevaría a clasificar erróneamente el evento como una ECM (experiencia cercana a la muerte). Los investigadores deben tener cuidado con estas clasificaciones erróneas. ^{[ 17 ]}

Moody describió que el enfoque correcto para un paciente de ECM es "Preguntar, Escuchar, Validar, Educar y Derivar". ^{[ 32 ]} Debido a la posible confusión o shock atribuido a quienes experimentan experiencias cercanas a la muerte, es importante tratarlos de manera tranquila y comprensiva justo después de su regreso de la ECM. Las ECM están asociadas con cambios en la personalidad y la perspectiva de la vida. ^{[ 7 ]} Ring ha identificado un conjunto consistente de cambios de valores y creencias asociados con las personas que han tenido una ECM. Entre estos cambios, encontró una mayor apreciación por la vida, mayor autoestima, mayor compasión por los demás, menor preocupación por adquirir riqueza material, un sentido de propósito y autocomprensión más elevado, deseo de aprender, espiritualidad elevada, mayor sensibilidad ecológica y preocupación planetaria, una sensación de ser más intuitivo, ^{[ 7 ]} ya no preocuparse por la muerte y afirmar haber presenciado una vida después de la muerte. ^{[ 33 ]} Aunque las personas que han experimentado ECM se vuelven más espirituales, no significa que se vuelvan necesariamente más religiosas. ^{[ 34 ]} No todos los efectos posteriores son beneficiosos, ^{[ 35 ]} y Greyson describe circunstancias en las que los cambios en las actitudes y el comportamiento pueden conducir a problemas psicosociales y psicoespirituales. ^{[ 36 ]}

Para establecer un marco de investigación riguroso para el estudio de las experiencias de encuentros con la muerte, las directrices de 2022 acordaron adoptar el término más preciso de experiencia recordada de la muerte ( RED ) en lugar de experiencia cercana a la muerte (NDE). ^{[ 17 ]} Una RED es una experiencia cercana a la muerte auténtica (véase Elementos comunes, Directrices de 2022 ). Por lo tanto, una RED se refiere a un evento cognitivo y emocional distinto que tiene lugar durante un período de pérdida de conciencia asociado con un episodio potencialmente mortal, como un paro cardíaco. ^{[ 17 ]} Las RED, al igual que las experiencias cercanas a la muerte auténticas, siguen el arco narrativo de las experiencias trascendentales originales de Moody ^{[ 17 ]} :

1. Una relación con la muerte.
2. Una sensación de trascender el mundo físico o material.
3. Inefabilidad
4. Cambios beneficiosos en la vida ligados a un sentido más profundo de significado y propósito.

REDs do not feature signs of the usual coma-associated phenomena like typical dreams, delirium, or delusional thinking.^[17] The term RED eliminates the vagueness of “near-death” by including both severe, life-threatening conditions that bring a person close to death (from a medical or pathophysiological standpoint) and states involving the actual physiological processes of death itself, such as cardiac arrest or other forms of cardiac standstill.^[17] The authors of the 2022 guidelines believe that focusing on REDs will provide a more robust research framework. Studies of REDs will avoid mixing distinct phenomena such as drug induced hallucinations, dreams, misattributed memories formed during emergence out of coma, etc.^[17]

NDEs have been recorded since ancient times.^[37] The oldest known medical report of near-death experiences was written by Pierre-Jean du Monchaux, an 18th-century French military doctor who described such a case in his book Anecdotes de Médecine.^[38] Monchaux hypothesized that an influx of blood in the brain stimulated a strong feeling in the individual, and therefore caused a near-death experience.^[38] In the 19th century a few studies moved beyond individual cases – one privately done by members of the Church of Jesus Christ of Latter-day Saints^[39] and one in Switzerland. Up to 2005, 95% of world cultures are known to have made some mention of NDEs.^[37]

In the U.S., an estimated nine million people have reported an NDE according to a 2011 study in Annals of the New York Academy of Sciences. Most of these near-death experiences resulted from serious injury affecting the body or brain.^[40] A number of more contemporary sources report the incidence of near death experiences as:

• 17% amongst critically ill patients, in nine prospective studies from four different countries.^[41]
• 10–20% of people who have come close to death.^[12]

Bruce Greyson (psychiatrist), Kenneth Ring (psychologist), and Michael Sabom (cardiologist), helped to launch the field of near-death studies and introduced the study of near-death experiences to the academic setting. From 1975 to 2005, some 2,500 self-reported individuals in the US had been reviewed in retrospective studies of the phenomena,^[37] with an additional 600 outside the US in the West,^[37] and 70 in Asia.^[37] Additionally, prospective studies had identified 270 individuals. Prospective studies review groups of individuals (e.g., selected emergency room patients) and then find who had an NDE during the study's time; such studies cost more to perform.^[37] In all, close to 3,500 individual cases between 1975 and 2005 had been reviewed in one or another study. All these studies were carried out by some 55 researchers or teams of researchers.^[37]

Melvin L. Morse, head of the Institute for the Scientific Study of Consciousness, and colleagues have investigated near-death experiences in a pediatric population.^[24][42][43] Researchers from the University of Michigan led by Jimo Borjigin discovered that areas of the brain responsible for interior visual experience were more active during cardiac arrest.^[44] Following the rapid gamma activation locally within the posterior TPO zones, the long-range, global, and interhemispheric communications in gamma oscillations between the TPO zones and the prefrontal areas were activated in the dying brain, evidenced by the delayed activation of temporofrontal, parietofrontal, and Occipitofrontal networks when heart rate began to decline. Intriguingly, the long-range gamma connectivity between the posterior hot zones and the prefrontal areas at near-death was significantly higher over baseline only for those crossing the midline. Studies suggest that interhemispheric circuitry is important for memory recall, and gamma synchrony across the midlines is critical for learning, information integration, and perception.^[44]

American radiation oncologist Jeffrey Long has amassed a large database of NDEs through the Near Death Experience Research Foundation (NDERF).^[45] 835 out of 1,122 people who had experienced NDE seemed to feel an increase in alertness and consciousness although studies proved no sign of electrical brain activity.^[46] His second line of evidence studies the increase of accuracy developed by NDErs defining their resuscitation process with a 97.6% accuracy rate.^[46] Long documented seven more lines of evidence that all point to realism in NDE experiences, yet not all of them verifiable or defined by today's medical advances and technology.^[46] Having such an abnormally large amount (95.6% of 1,000 participants) of those who had experienced NDE proclaiming NDEs as real experiences, he concludes that although NDE are medically inexplicable, they are most probably a real phenomenon.^[46]

According to literature, the field of near-death studies is associated with discovery, challenges, and controversy.^[47] Cant and colleagues note that "curiosity about the origin and prevalence of NDEs has escalated as technology and resuscitation techniques have improved".^[48] The topic attracts a lot of interest, which is reflected in search engine results, medical literature, opinion pieces and commentary. Kopel and Webb note that there has been a "burgeoning literature on near-death experiences", reflecting both the naturalistic perspectives of neurology and physiology, as well as perspectives that are not naturalistic.^[49] Skepticism towards the findings of near-death studies, and the validity of the near-death experience as a subject for scientific study, has been widespread. According to Knapton, in The Daily Telegraph,^[50] the subject was, until recently, controversial. Both scientists and medical professionals have in general tended to be skeptical.^{[51][52][53][54]} According to commentators in the field, the early study of near-death experiences was met with "academic disbelief".^[55] Acceptance of NDEs as a legitimate topic for scientific study has improved,^[51] but the process has been slow.^[56]

According to literature, "psychiatrists have played a role in the recognition of the "near-death" phenomenon as well as popularization of the subject and subsequent research".^[57] Kinsella noted that "Growing scholarly interest has followed popular interest in the subject".^[58] While there is not yet any academic consensus as to what the philosophical implications of NDE studies might be, the question of whatever the true and fundamental nature of human consciousness might be yet remains both unanswered, and highly contentious. Still, NDE researchers are in general agreement that NDE research is now a legitimate academic field of scientific research, and many recent discoveries in this field give rise to the hopes by some researchers that a "breakthrough" in the modern day understanding of the dying process may be imminent.^[59]

Kovoor and colleagues noted that there are some "methodological concerns within many of the prospective studies" mapped by their scoping review. They further observed: "Longer-term outcomes may have been biased by clinical characteristics and comorbidities, rather than near-death experiences, and this should remain a pertinent consideration."^[60] Skeptics have remarked that it is difficult to verify many of the anecdotal reports that are being used as background material in order to outline the features of the NDE.^[51][61] The findings of NDE research have been contested by several writers in the fields of psychology and neuroscience.^[61] Criticism of the field has also come from commentators within its own ranks. In an open letter to the NDE community, Ring has pointed to the "issue of possible religious bias in near-death studies". According to Ring, the field of near-death studies, as well as the larger NDE movement, has attracted a variety of religious and spiritual affiliations, from a number of traditions, which makes ideological claims on behalf of NDE research. In his view, this has compromised the integrity of research and discussion.^[62]

A 2021 study of 101 patients that underwent Deep hypothermic circulatory arrest found that none of them had anything that could be described as a Near-Death Experience.^[63]

En 2001, Sam Parnia y sus colegas publicaron los resultados de un estudio de un año de duración sobre supervivientes de paro cardíaco realizado en el Hospital General de Southampton. Se entrevistó a 63 supervivientes. Habían sido reanimados tras estar clínicamente muertos, sin pulso, sin respiración y con pupilas fijas dilatadas. Parnia y sus colegas investigaron las afirmaciones de experiencias extracorporales colocando figuras en áreas donde era probable que los pacientes fueran reanimados, sobre paneles suspendidos orientados hacia el techo, no visibles desde el suelo. Cuatro tuvieron experiencias que, según los criterios del estudio, eran ECM, pero ninguno de ellos experimentó la experiencia extracorporal. Por lo tanto, no pudieron identificar las figuras. ^{[ 64 ] [ 26 ] [ 65 ]} El psicólogo Chris French escribió sobre el estudio: «Desafortunadamente, y de forma algo atípica, ninguno de los supervivientes de esta muestra experimentó una experiencia extracorporal». ^{[ 26 ]}

En 2001, Pim van Lommel , cardiólogo de los Países Bajos, y su equipo realizaron un estudio sobre las ECM (experiencias cercanas a la muerte) que incluyó a 344 pacientes con paro cardíaco que habían sido reanimados con éxito en 10 hospitales holandeses. Los pacientes que no informaron de ECM se utilizaron como grupo de control para los pacientes que sí las informaron, y se compararon datos psicológicos (p. ej., miedo antes del paro cardíaco), demográficos (p. ej., edad, sexo), médicos (p. ej., más de una reanimación cardiopulmonar (RCP)) y farmacológicos entre los dos grupos. ^{[ 66 ]}

El trabajo también incluyó un estudio longitudinal donde se compararon los dos grupos (aquellos que habían tenido una ECM y aquellos que no) a los dos y ocho años, para observar los cambios en sus vidas. Un paciente tuvo una experiencia extracorporal convencional. Informó haber podido observar y recordar eventos durante el tiempo de su paro cardíaco. Sus afirmaciones fueron confirmadas por el personal del hospital. "Esto no parecía ser consistente con experiencias alucinatorias o ilusorias, ya que los recuerdos eran compatibles con eventos reales y verificables en lugar de eventos imaginados". ^{[ 65 ] [ 66 ]}

While at the University of Southampton, Parnia was the principal investigator of the AWARE Study, which was launched in 2008.^[13] The study, which concluded in 2012, included 33 investigators across 15 medical centers in the UK, Austria and the US and tested consciousness, memories and awareness during cardiac arrest. The accuracy of claims of visual and auditory awareness was examined using specific tests.^[67] One such test consisted of installing shelves, bearing a variety of images and facing the ceiling, hence not visible to hospital staff, in rooms where cardiac-arrest patients were more likely to occur. The results of the study were published in October 2014.^[68][69]

A review article analyzing the results reports that, out of 2,060 cardiac arrest events, 101 of 140 cardiac arrest survivors could complete the questionnaires. Of these 101 patients, 9% could be classified as near-death experiences. Two more patients (2% of those completing the questionnaires) described "seeing and hearing actual events related to the period of cardiac arrest". These two patients' cardiac arrests did not occur in areas equipped with ceiling shelves, hence no images could be used to objectively test for visual awareness claims. One of the two patients was too sick and the accuracy of her recount could not be verified. For the second patient, however, it was possible to verify the accuracy of the experience and to show that awareness occurred paradoxically some minutes after the heart stopped, at a time when "the brain ordinarily stops functioning and cortical activity becomes isoelectric (i.e., without any discernible electric activity)." The experience was not compatible with an illusion, imaginary event or hallucination since visual (other than of ceiling shelves' images) and auditory awareness could be corroborated.^[65]

As of May 2016, a posting at the UK Clinical Trials Gateway website described plans for AWARE II, a two-year multicenter observational study of 900–1,500 patients experiencing cardiac arrest, which said that subject recruitment had started on 1 August 2014 and that the scheduled end date was 31 May 2017.^[70] The study was extended, continuing until 2020.^[71] In 2019, a report of a condensed version of the study with 465 patients was released. Only one patient remembered the auditory stimuli while none remembered the visual.^[72] In November 2022, the full study was published.^[73]

En un artículo de revisión de 2005, el psicólogo Chris French clasificó los modelos que intentan explicar las ECM en tres grandes grupos que "no son distintos ni independientes, sino que muestran una considerable superposición": espirituales (o trascendentales), psicológicos y fisiológicos. ^{[ 26 ]}

French resume este modelo diciendo: «la interpretación más popular es que la ECM es exactamente lo que parece ser para la persona que la experimenta». ^{[ 26 ]} La ECM representaría evidencia de la existencia inmaterial de un alma o mente, que abandona el cuerpo al morir y proporciona información sobre un mundo inmaterial al que el alma viaja después de la muerte. ^{[ 26 ]}

Según Greyson, algunos fenómenos de las ECM no se pueden explicar fácilmente con nuestro conocimiento actual de la fisiología y la psicología humanas. Por ejemplo, en un momento en que estaban inconscientes, los pacientes podían describir con precisión eventos "desde una perspectiva espacial extracorpórea". ^{[ 12 ]} En dos estudios diferentes de pacientes que habían sobrevivido a un paro cardíaco, aquellos que habían informado haber abandonado sus cuerpos podían describir con precisión sus procedimientos de reanimación o eventos inesperados, mientras que otros "describieron equipos y procedimientos incorrectos". ^{[ 12 ]} Sam Parnia también se refiere a dos estudios de paro cardíaco y un estudio de paro circulatorio con hipotermia profunda donde los pacientes informaron conciencia visual y/o auditiva que ocurrió cuando su función cerebral había cesado. Estos informes "fueron corroborados con eventos reales y reales". ^{[ 74 ] [ 65 ]}

Se han realizado cinco estudios prospectivos para comprobar la exactitud de las percepciones extracorporales colocando "objetivos inusuales en lugares que probablemente vean las personas que experimentan ECM, como en la esquina superior de una habitación en el servicio de urgencias, la unidad de cuidados coronarios o la unidad de cuidados intensivos de un hospital". Doce pacientes informaron haber abandonado sus cuerpos, pero ninguno pudo describir los objetivos visuales ocultos. Aunque se trata de una muestra pequeña, el hecho de que quienes afirman haber tenido experiencias extracorporales no hayan podido describir los objetivos ocultos plantea dudas sobre la exactitud de los relatos anecdóticos descritos anteriormente. ^{[ 12 ]}

La neurocientífica Charlotte Martial afirma que hay una escasez de evidencia empírica sólida sobre las teorías de la conciencia no local, ^{[ 75 ]} lo cual es sostenido por algunos autores. ^{[ 76 ] [ 77 ]} Chris French ha señalado que "el enfoque de supervivencia no parece generar hipótesis claras y comprobables. Debido a la vaguedad e imprecisión de la explicación de supervivencia, puede utilizarse para explicar cualquier conjunto posible de hallazgos y, por lo tanto, es infalsificable y acientífico". ^{[ 78 ]}

French resume las principales explicaciones psicológicas, que incluyen los modelos de despersonalización, expectativa y disociación. ^{[ 26 ]}

En la década de 1970, el profesor de psiquiatría Russell Noyes y el psicólogo clínico Roy Kletti propusieron un modelo de despersonalización que sugería que la ECM es una forma de despersonalización , experimentada bajo condiciones emocionales como peligro mortal, peligro potencialmente ineludible, y que la ECM se entiende mejor como una alucinación . ^{[ 26 ] [ 79 ] [ 80 ] [ 81 ] [ 82 ]} Según este modelo, quienes se enfrentan a su muerte inminente se desapegan psicológicamente de su entorno y de sus cuerpos, dejan de sentir emociones y experimentan distorsiones temporales. ^{[ 12 ]}

Este modelo presenta varias limitaciones para explicar las ECM en sujetos que no experimentan la sensación de estar fuera de su cuerpo; a diferencia de las ECM, estas experiencias alucinatorias son oníricas, desagradables y se caracterizan por "ansiedad, pánico y vacío". ^{[ 12 ]} Además, durante las ECM los sujetos conservan una gran lucidez respecto a su identidad, y su sentido de identidad no se altera, a diferencia de quienes experimentan despersonalización. ^{[ 12 ]}

Another psychological theory is called the expectancy model. It has been suggested that although these experiences could appear very real, they had actually been constructed in the mind, either consciously or subconsciously, in response to the stress of an encounter with death (or perceived encounter with death), and did not correspond to a real event. In a way, they are similar to wish-fulfillment: because someone thought they were about to die, they experienced certain things in accordance with what they expected or wanted to occur. Imagining a heavenly place was, in effect, a way for them to soothe themselves through the stress of knowing that they were close to death.^[26] Subjects use their own personal and cultural expectations to imagine a scenario that would protect them against an imminent threat to their lives.^[12]

Subjects' accounts often differed from their own "religious and personal expectations regarding death", which contradicts the hypothesis they may have imagined a scenario based on their cultural and personal background.^[12] Although the term NDE was first coined in 1975 and the experience first described then, recent descriptions of NDEs do not differ from those reported earlier than 1975. The only exception is the more frequent description of a tunnel. Hence, the fact that information about these experiences could be more easily obtained after 1975 had not influenced people's reports of the experiences.^[12] Another flaw of this model can be found in children's accounts of NDEs. These are similar to adults', despite children being less strongly affected by religious and cultural influences about death.^[12]

The dissociation model proposes that NDE is a form of withdrawal to protect an individual from a stressful event. Under extreme circumstances, some people may detach from certain unwanted feelings in order to avoid experiencing the emotional impact and suffering associated with them. The person also detaches from one's immediate surroundings.^[26]

The birth model suggests that near-death experiences could be a form of reliving the trauma of birth. Since a baby travels from the darkness of the womb to light and is greeted by the love and warmth of the nursing and medical staff, and so, it was proposed, the dying brain could be recreating the passage through a tunnel to light, warmth and affection.^[26] Reports of leaving the body through a tunnel are equally frequent among subjects who were born by cesarean section and natural birth. Newborns do not possess "the visual acuity, spatial stability of their visual images, mental alertness, and cortical coding capacity to register memories of the birth experience".^[12]

A wide range of physiological theories of the NDE have been put forward, including those based upon cerebral hypoxia, anoxia, and hypercapnia; endorphins and other neurotransmitters; and abnormal activity in the temporal lobes.^[26]Neurobiological factors in the experience have been investigated by researchers in the field of medical science and psychiatry.^[83] Among the researchers and commentators who tend to emphasize a naturalistic and neurological base for the experience is the British psychologist Susan Blackmore (1993), with her "dying brain hypothesis".^[84]

According to Greyson,^[12] multiple neuroanatomical models have been proposed, wherein NDEs have been hypothesized to originate from different anatomical areas of the brain, namely: the limbic system, the hippocampus, the left temporal lobe, Reissner's fiber in the central canal of the spinal cord, the prefrontal cortex, and the right temporal lobe. Neuroscientists Olaf Blanke and Sebastian Dieguez (2009),^[85] from the Ecole Polytechnique Fédérale de Lausanne, Switzerland, propose a brain-based model with two types of NDEs:

• "type 1 NDEs are due to bilateral frontal and occipital, but predominantly right hemispheric brain damage affecting the right temporal-parietal junction and characterized by out-of-body-experiences, altered sense of time, sensations of flying, lightness vection and flying"^[4]
• "type 2 NDEs are also due to bilateral frontal and occipital, but predominantly left hemispheric brain damage affecting the left temporal parietal junction and characterized by feeling of a presence, meeting and communication with spirits, seeing of glowing bodies, as well as voices, sounds, and music without vection"^[4]

They suggest that damage to the bilateral occipital cortex may lead to visual features of NDEs such as seeing a tunnel or lights, and "damage to unilateral or bilateral temporal lobe structures such as the hippocampus and amygdala" may lead to emotional experiences, memory flashbacks or a life review. They concluded that future neuroscientific studies are likely to reveal the neuroanatomical basis of the NDE, which will lead to the demystification of the subject without needing paranormal explanations.^[4]

French has written that the "temporal lobe is almost certain to be involved in NDEs, given that both damage to and direct cortical stimulation of this area are known to produce a number of experiences corresponding to those of the NDE, including OBEs, hallucinations, and memory flashbacks".^[26] Vanhaudenhuyse et al. (2009) reported that recent studies employing deep brain stimulation and neuroimaging have demonstrated that out-of-body experiences can result from a deficient multisensory integration at the temporal-parietal junction and that ongoing studies aim to further identify the functional neuroanatomy of near-death experiences by means of standardized EEG recordings.^[86]

Blanke et al.^[4] admit that their model remains speculative due to the lack of data. In addition, the reports of those who had the brain stimulation were almost nothing like OBEs reported by those who had NDEs, mainly characterized by a sense of elevation and (often limited) spatial awareness, while other characteristics of NDEs were absent. Anomalies such as seeing maps, half-bodies and duplications were also noted.^[87][88] Likewise, Greyson writes that although some, or any of the proposed neuroanatomical models may serve to explain NDEs and pathways through which they are expressed, they remain speculative at this stage, since they have not been tested in empirical studies.^[12]

Some theories explain reported NDE experiences as resulting from drugs used during resuscitation (in the case of resuscitation-induced NDEs) ─ for example, ketamine ─ or from endogenous chemicals (neurotransmitters) that transmit signals between brain cells:^[26]

• In the early 1980s, Daniel Carr wrote that the NDE has characteristics that are suggestive of a limbic lobe syndrome and that the NDE can be explained by the release of endorphins and enkephalins in the brain.^[89][90] Endorphins are endogenous molecules "released in times of stress and lead to a reduction in pain perception and a pleasant, even blissful, emotional state."^[26]
• Judson and Wiltshaw (1983) noted how the administration of endorphin-blocking agents such as naloxone had been occasionally reported to produce "hellish" NDEs.^[91] This would be coherent with endorphins' role in causing a "positive emotional tone of most NDEs".^[26]
• Morse et al. (1989) proposed a model arguing that serotonin played a more important role than endorphins in generating NDEs,^[92] "at least with respect to mystical hallucinations and OBEs".^[26]
• A 2019 large-scale study found that ketamine, Salvia divinorum, and DMT (and other classical psychedelic substances) are linked to near-death experiences.^[93]
• While ketamine, and other endogenous chemicals can be a source for NDE, it can also mimic these NDE and simulate that out-of-body experiences linked to NDE.^[94]

According to Parnia, neurochemical models are not backed by data. This is true for "NMDA receptor activation, serotonin, and endorphin release" models.^[65] Parnia writes that no data has been collected via thorough and careful experimentation to back "a possible causal relationship or even an association" between neurochemical agents and NDE experiences.^[74]

The first formal neurobiological model for NDEs in 1989 included endorphins, neurotransmitters of the limbic system, the temporal lobe and other parts of the brain.^[95] Extensions and variations of their model came from other scientists such as Louis Appleby (1989).^[96] Other authors suggest that all components of near-death experiences can be explained in their entirety via psychological or neurophysiological mechanisms, although the authors admit that these hypotheses have to be tested by science.^[23]

Low oxygen levels in the blood (hypoxia or anoxia) have been hypothesized to induce hallucinations and hence possibly explain NDEs.^[2][26] This is because low oxygen levels characterize life-threatening situations and also the apparent similarities between NDEs and G-force-induced loss of consciousness (G-LOC) episodes. These episodes are observed with fighter pilots experiencing very rapid and intense acceleration that results in lack of sufficient blood supply to the brain. Whinnery^[97] studied almost 1000 cases and noted how the experiences often involved "tunnel vision and bright lights, floating sensations, automatic movement, autoscopy, OBEs, not wanting to be disturbed, paralysis, vivid dreamlets of beautiful places, pleasurable sensations, psychological alterations of euphoria and dissociation, inclusion of friends and family, inclusion of prior memories and thoughts, the experience being very memorable (when it can be remembered), confabulation, and a strong urge to understand the experience."^[26][97]

Acceleration-induced hypoxia's primary characteristics are "rhythmic jerking of the limbs, compromised memory of events just prior to the onset of unconsciousness, tingling of extremities ..." that are not observed during NDEs.^[2] G-LOC episodes do not feature life reviews, mystical experiences and "long-lasting transformational aftereffects", although this may be due to the fact that subjects have no expectation of dying.^[26] Hypoxic hallucinations are characterized by "distress and agitation", and this is very different from near-death experiences, which subjects usually report as being pleasant.^[12]

Some investigators have studied whether hypercarbia or higher than normal carbon dioxide levels, could explain the occurrence of NDEs. However, studies are difficult to interpret since NDEs have been observed both with increased levels as well as decreased levels of carbon dioxide, and other studies have observed NDEs when levels had not changed, but there is insufficient data on these factors.^[2]

French said that at least some reports of NDEs might be based upon false memories.^[98] According to Engmann (2008), near-death experiences of people who are clinically dead are psychopathological symptoms caused by a severe malfunction of the brain resulting from the cessation of cerebral blood circulation.^[99] An important question is whether it is possible to "translate" the bloomy experiences of the reanimated survivors into psychopathologically basic phenomena, e.g., acoasms (nonverbal auditory hallucinations), central narrowing of the visual field, autoscopia, visual hallucinations, activation of limbic and memory structures (according to Moody's stages). The symptoms suppose a primary affliction of the occipital and temporal cortices under clinical death. This basis could be congruent with the thesis of pathoclisis – the inclination of special parts of the brain to be the first to be damaged in case of disease, lack of oxygen, or malnutrition – established in 1922 by Cécile Vogt-Mugnier and Oskar Vogt.^[100]

Professor of neurology Terence Hines (2003) claimed that near-death experiences are hallucinations caused by cerebral anoxia, drugs, or brain damage.^[101] Greyson has called into question the adequacy of the materialist, mind-brain identity model for explaining NDEs.^[22] An NDE often involves vivid and complex mentation, sensation and memory-formation under circumstances of completely disabled brain function during general anesthesia, or near-complete cessation of cerebral blood flow and oxygen uptake during cardiac arrest. Materialist models predict that such conscious experiences should be impossible under these conditions. The mind-brain identity model of classic materialist psychology may need to be expanded to adequately explain an NDE.

• After-death communication – Spiritual practicePages displaying short descriptions of redirect targets
• Beyond and Back – 1978 film
• Cognitive science of religion – Study of religious thought and behavior
• Deathbed phenomena – Range of experiences reported by dying people
• Deism – Belief in a god based on rational thought
• Form constant – Recurringly observed geometric pattern
• Lazarus syndrome – Medical phenomenon
• Near-birth experience – Alleged recollected event which occurred before or during one's own birth
• Neurotheology – Attempts to explain religious experience in neuroscientific termsPages displaying short descriptions of redirect targets
• Out-of-body experience – Phenomenon in which the soul (astral body) is said to exit the physical body
• Pam Reynolds case – Reported near-death experience
• Passage (Willis novel) – 2001 novel by Connie Willis
• Proof of Heaven – 2012 nonfiction book by Eben Alexander
• Psychedelic experience – Altered state of consciousness
• Resurrection – Concept of coming back to life
• Saved by the Light – 1994 book by Dannion Brinkley
• Terminal lucidity – Sign of impending death
• Zendegi Pas Az Zendegi – Iranian reality TV series (2020–2023)

• Alcock, James (1979). "Psychology and Near-Death Experiences". Skeptical Inquirer. 3: 25–41.
• Lee Worth Bailey; Jenny Yates. (1996). The Near-Death Experience: A Reader. Routledge. ISBN 0-415-91431-0
• Blackmore, Susan (2002). "Near-Death Experiences". In Shermer, Ed. M. (ed.). The Skeptic Encyclopedia of Pseudoscience. Santa Barbara, CA.: ABC-Clio. pp. 152–157. ISBN 978-1-57607-653-8.
• Carroll, Robert T. (12 September 2014). "Near-death experience (NDE)". The Skeptic's Dictionary. Retrieved 21 August 2017.
• Choi, Charles Q. (September 12, 2011). "Peace of Mind: Near-Death Experiences Now Found to Have Scientific Explanations". Scientific American.
• Engmann, Birk (2014). Near-death experiences: heavenly insight or human illusion?. Imprint: Springer. ISBN 978-3-319-03727-1.{{cite book}}: CS1 maint: publisher location (link)
• Fenwick, Peter; Fenwick, Elizabeth (1995). The Truth in the Light. Berkley Books, New York. ISBN 0-425-15608-7.
• Bruce Greyson, Charles Flynn. (1984). The Near-Death Experience: Problems, Prospects, Perspectives. Springfield. ISBN 0-398-05008-2
• Perera, Mahendra; Jagadheesan, Karuppiah; Peake, Anthony, eds. (2012). Making sense of near-death experiences: a handbook for clinicians. London: Jessica Kingsley Publishers. ISBN 978-1-84905-149-1.
• Ring, Kenneth; Elsaesser, Evelyn (2024-07-08). Lessons from the Light: What Near-Death Experiences Teach Us about Living in the Here and Now. Red Wheel Weiser. ISBN 978-1-63748-018-2.
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• Shermer, Michael (April 1, 2013). "Proof of Hallucination". Scientific American. 308 (4): 86. Bibcode:2013SciAm.308d..86S. doi:10.1038/scientificamerican0413-86. PMID 23539795.
• Schlieter, Jens (2018). What is it like to be dead?: Near-death experiences, Christianity, and the Occult times (Hardcover ed.). New York: Oxford University Press. ISBN 978-0-19-088884-8.
• van Lommel, Pim (2010). After life: a scientific approach to near-death experiences (1st ed.). New York: HarperOne. ISBN 978-0-06-177725-7.
• Woerlee, G.M. (May 2004). "Darkness, Tunnels, and Light". Skeptical Inquirer. 28 (3).
• Woerlee, G.M. (2005). Mortal minds: the biology of near-death experiences. Amherst, NY: Prometheus Books. ISBN 978-1-59102-283-1.
• Zaleski, Carol (1987). Otherworld journeys: accounts of near-death experience in medieval and modern times (Paperback ed.). New York: Oxford University Press. ISBN 978-0-19-503915-3.

• Intelligence Squared debate on NDE featuring Eben Alexander, Raymond Moody, Sean Carroll, and Steven Novella
• International Association for Near-Death Studies (IANDS)
• The Skeptic's Dictionary entry on NDE