NDEs are among the phenomena studied in the fields of parapsychology, psychology, psychiatry, and hospital medicine.

Popular interest in near-death experiences was initially sparked by Raymond Moody’s 1975 book Life After Life and the founding of the International Association for Near-Death Studies (IANDS) in 1981. According to a Gallup poll, approximately eight million Americans claim to have had a near-death experience.

Some commentators, such as Simpson claim that the number of near-death experiencers may be underestimated, mainly because some such individuals are presumably afraid or otherwise reluctant to talk about their experiences.

The earliest accounts of NDE can be traced to the Myth of Er, recorded by Plato’s The Republic (10.614-10.621). In this story, Plato describes a mythical soldier telling of his near-death experiences about an afterlife and reincarnation.

Researchers have identified the common elements that define near-death experiences. Bruce Greyson argues that the general features of the experience include impressions of being outside one’s physical body, visions of deceased relatives and religious figures, and transcendence of ego and spatiotemporal boundaries. The experience may also follow a distinct progression, as illustrated below.

The traits of a classical NDE are as follows:

1 – Receiving messages in telepathic form.
2 – A sense/awareness of being dead.
3 – A sense of peace, well-being and painlessness. Positive emotions. A feeling of being removed from the world.
4 – An out-of-body experience. A perception of one’s body from an outside position. Sometimes observing doctors and nurses performing medical resuscitation efforts.
5 – A “tunnel experience”. A sense of moving up, or through, a passageway or staircase.A rapid movement toward and/or sudden immersion in a powerful light. Communication with the light.
6 – An intense feeling of unconditional love.
7 – Encountering “Beings of Light”, “Beings dressed in white”, or other spiritual beings. Also, the possibility of being reunited with deceased loved ones.
8 – Being given a life review.
9 – Being presented with knowledge about one’s life and the nature of the universe.
10 – A decision by oneself or others to return to one’s body, often accompanied by a reluctance to return.
11- Approaching a border.
12 – There also seems to be a link between the cultural and spiritual beliefs where one lives. These seem to dictate what is experienced in the NDE or how it is interpreted afterwards (Holden, Janice Miner. Handbook of Near-Death Experiences. Library of Congress Cataloging in Publishing Data, 2009.).
Kenneth Ring (1980) subdivided the NDE on a five-stage continuum. He stated that 60% experienced stage 1 (feelings of peace and contentment), but only 10% experienced stage 5 (“entering the light”).

Clinical circumstances associated with near-death experiences include cardiac arrest in myocardial infarction (clinical death), shock in postpartum loss of blood or in perioperative complications, septic or anaphylactic shock, electrocution, coma resulting from traumatic brain damage, intracerebral hemorrhage or cerebral infarction, attempted suicide, near-drowning or asphyxia, apnea, and serious depression. In contrast to common belief, Kenneth Ring argues that attempted suicides do not lead more often to unpleasant NDEs than unintended near-death situations.

The distressing aspects of some NDEs are discussed more closely by Greyson and Bush. Karlis Osis and his colleague Erlendur Haraldsson argued that the content of near death experiences does not vary by culture, except for the identity of the personages and religious figures seen during the experiences; however Yoshi Hata and his team reported NDEs with substantially different contents than those described above.

Contributions to the research on near-death experiences have come from several academic disciplines, among these the disciplines of medicine, psychology and psychiatry. Interest in this field of study was originally spurred by the research of such pioneers as Elisabeth Kübler-Ross, George Ritchie, and Raymond Moody Jr. Moody’s book Life After Life, which was released in 1975, brought a lot of attention to the topic of NDEs.

This was soon to be followed by the establishment of the International Association for Near-death Studies (IANDS) in 1981. IANDS is an international organization that encourages scientific research and education on the physical, psychological, social, and spiritual nature and ramifications of near-death experiences. Among its publications are the peer-reviewed Journal of Near-Death Studies and the quarterly newsletter Vital Signs.

Later researchers, such as Bruce Greyson, Kenneth Ring, and Michael Sabom, helped to launch the field of Near-Death Studies and introduced the study of near-death experiences to the academic setting.

The medical community has been somewhat reluctant to address the phenomenon of NDEs, and grant money for research has been scarce. However, both Greyson and Ring developed tools that can be used in a clinical setting. Major contributions to the field include Ring’s construction of a “Weighted Core Experience Index” to measure the depth of the near-death experience and Greyson’s construction of the “Near-death experience scale” to differentiate between subjects that are more or less likely to have experienced an NDE. The latter scale is also, according to its author, clinically useful in differentiating NDEs from organic brain syndromes and nonspecific stress responses. The NDE-scale was later found to fit the Rasch rating scale model.

Greyson has also brought attention to the near-death experience as a focus of clinical attention, while Morse and colleagues have investigated near-death experiences in a pediatric population.

Neuro-biological factors in the experience have been investigated by researchers in the field of medical science and psychiatry. Among the researchers and commentators who tend to emphasize a naturalistic and neurological base for the experience are the British psychologist Susan Blackmore (1993), with her “dying brain hypothesis”, and the founding publisher of Skeptic magazine, Michael Shermer (1998).

In September 2008 it was announced that 25 UK and US hospitals will examine near-death studies in 1,500 heart attack patient-survivors. The three-year study, coordinated by Dr. Sam Parnia at Southampton University, hopes to determine if people without heartbeat or brain activity can have an out-of-body experience with veridical visual perceptions. This study follows on from an earlier 18-month pilot project.

On a July 28, 2010 interview about a recent lecture at Goldsmiths, Parnia asserts that “evidence is now suggesting that mental and cognitive processes may continue for a period of time after a death has started” and describes the process of death as “essentially a global stroke of the brain.

Therefore like any stroke process one would not expect the entity of mind / consciousness to be lost immediately”. He also expresses his disagreement with the term ‘near death experiences’ because “the patients that we study are not near death, they have actually died and more over it conjures up a lot of imprecise scientific notions, due to the fact that itself is a very imprecise term”.

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Among the scientific and academic journals that have published, or are regularly publishing, new research on the subject of NDEs are Journal of Near-Death Studies, Journal of Nervous and Mental Disease, British Journal of Psychology, American Journal of Disease of Children, Resuscitation, The Lancet, Death Studies, and the Journal of Advanced Nursing.

The prevalence of NDEs has been variable in the studies that have been performed. According to the Gallup and Proctor survey in 1980-1981, of a representative sample of the American population, data showed that 15% had an NDE. Knoblauch in 2001 performed a more selective study in Germany and found that 4% of the sample population had experienced an NDE. However, the information gathered from these studies may be subjected to the broad timeframe and location of the investigation.

Perera et al., in 2005, conducted a telephone survey of a representative sample of the Australian population, as part of the Roy Morgan Catibus Survey, and concluded that 8.9% of the population had experienced an NDE.

In a more clinical setting, van Lommel et al. (2001), a cardiologist from Netherlands, studied a group of patients who had suffered cardiac arrests and who were successfully revived. They found that 62 patients (18%) had an NDE, of whom 41 (12%) described a core experience.

According to Martens the only satisfying method to address the NDE-issue would be an international multicentric data collection within the framework for standardized reporting of cardiac arrest events. The use of cardiac-arrest criteria as a basis for NDE research has been a common approach among the European branch of the research field.

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In the 1990s, Dr. Rick Strassman conducted research on the psychedelic drug Dimethyltryptamine (DMT) at the University of New Mexico.

Strassman advanced the theory that a massive release of DMT from the pineal gland prior to death or near-death was the cause of the near-death experience phenomenon.

Only two of his test subjects reported NDE-like aural or visual hallucinations, although many reported feeling as though they had entered a state similar to the classical NDE. His explanation for this was the possible lack of panic involved in the clinical setting and possible dosage differences between those administered and those encountered in actual NDE cases.

All subjects in the study were also very experienced users of DMT and/or other psychedelic/entheogenic agents. Some speculators consider that if subjects without prior knowledge on the effects of DMT had been used during the experiment, it is possible more volunteers would have reported feeling as though they had experienced an NDE.

Critics have argued that neurobiological models often fail to explain NDEs that result from close brushes with death, where the brain does not actually suffer physical trauma, such as a near-miss automobile accident. Such events may however have neurobiological effects caused by stress.

In a new theory devised by Richard Kinseher in 2006, the knowledge of the Sensory Autonomic System is applied in the NDE phenomenon. His theory states that the experience of looming death is an extremely strange paradox to a living organism—and therefore it will start the NDE: during the NDE, the individual becomes capable of “seeing” the brain performing a scan of the whole episodic memory (even prenatal experiences), in order to find a stored experience which is comparable to the input information of death.

All these scanned and retrieved bits of information are permanently evaluated by the actual mind, as it is searching for a coping mechanism out of the potentially fatal situation. Kinseher feels this is the reason why a near-death experience is so unusual. Because people who experience NDEs report the experience of memories long considered lost, this theory necessarily depends upon a theory of memory in which all memories are indefinitely retained. Such a stance would be at odds with current scientific findings.

The theory also states that out-of-body experiences, accompanied by NDEs, are an attempt by the brain to create a mental overview of the situation and the surrounding world. The brain then transforms the input from sense organs and stored experience (knowledge) into a dream-like idea about oneself and the surrounding area.

Whether or not these experiences are hallucinatory, they do have a profound impact on the observer. Many psychologists not necessarily pursuing the paranormal, such as Susan Blackmore, have recognized this. These scientists are not trying to debunk the experience, but are instead searching for biological causes of NDEs.

According to Engmann, 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.

An important question is whether it is possible to “translate” the bloomy experiences of the reanimated survivors into psychopathologically basic phenomena, e.g. acoasms, 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 eighty years ago by C. and O. Vogt.

According to that thesis, the basic phenomena should be similar in all patients with near-death experiences. But a crucial problem is to distinguish these basic psychopathological symptoms from the secondary mental associated experiences which may result from a reprocessing of the basic symptoms under the influence of the person’s cultural and religious views.

An article by Netherlands researchers Pim van Lommel et al., argues, “With a purely physiological explanation such as cerebral anoxia for the experience, most patients who have been clinically dead should report one.” Accordingly, a lack of predictable experiences should cast doubt on wholesale explanations of NDEs.

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