Some people who have survived a life-threatening crisis report an extraordinary experience. Near-death experience occurs with increasing frequency because of improved survival rates resulting from modern techniques of resuscitation.
The content of NDE and the effects on patients seem similar worldwide, across all cultures and times. The subjective nature and absence of a frame of reference for this experience lead to individual, cultural, and religious factors determining the vocabulary used to describe and interpret the experience.1
NDE are reported in many circumstances: 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, and apnea.
Such experiences are also reported by patients with serious but not immediately life-threatening diseases, in those with serious depression, or without clear cause in fully conscious people. Similar experiences to near-death ones can occur during the terminal phase of illness, and are called deathbed visions.
Identical experiences to NDE, so-called fear-death experiences, are mainly reported after situations in which death seemed unavoidable: serious traffic accidents, mountaineering accidents, or isolation such as with shipwreck.
Several theories on the origin of NDE have been proposed. Some think the experience is caused by physiological changes in the brain, such as brain cells dying as a result of cerebral anoxia.2-4 Other theories encompass a psychological reaction to approaching death,5 or a combination of such reaction and anoxia.6
Such experiences could also be linked to a changing state of consciousness (transcendence), in which perception, cognitive functioning, emotion, and sense of identity function independently from normal body-linked waking consciousness.7
People who have had an NDE are psychologically healthy; although some show non-pathological signs of dissociation.7 Such people do not differ from controls with respect to age, sex, ethnic origin, religion, or degree of religious belief.1
Studies on NDE1,3,8,9 have been retrospective and very selective with respect to patients. In retrospective studies, 5-10 years can elapse between occurrence of the experience and its investigation, which often prevents accurate assessment of physiological and pharmacological factors.
In retrospective studies, about 45%1 of adults and up to 85% of children10 who had a life-threatening illness were estimated to have had an NDE. A random investigation of more than 2000 Germans showed 43% to have had an NDE at a mean age of 22 years.11
Differences in estimates of frequency and uncertainty as to causes of this experience result from varying definitions of the phenomenon, and from inadequate methods of research.12
Patients' transformational processes after an NDE are very similar1,3,13-16 and encompass life-changing insight, heightened intuition, and disappearance of fear of death. Assimilation and acceptance of these changes is thought to take at least several years.15
The authors defined NDE as the reported memory of all impressions during a special state of consciousness, including specific elements such as out-of-body experience, pleasant feelings, and seeing a tunnel, a light, deceased relatives, or a life review.
They defined clinical death as a period of unconsciousness caused by insufficient blood supply to the brain because of inadequate blood circulation, breathing, or both. If, in this situation, CPR is not started within 5-10 min, irreparable damage is done to the brain and the patient will die.
The results show that medical factors cannot account for occurrence of NDE; although all patients had been clinically dead, most did not have NDE. Furthermore, seriousness of the crisis was not related to occurrence or depth of the experience.
If purely physiological factors resulting from cerebral anoxia caused NDE, most of the patients should have had this experience. Patients' medication was also unrelated to frequency of NDE. Psychological factors are unlikely to be important as fear was not associated with NDE.
Only 12% of patients had a core NDE, and this figure might be an overestimate. True frequency of the experience is likely to be about 10%, or 5% if based on number of resuscitations rather than number of resuscitated patients. Patients who survive several CPRs in hospital have a significantly higher chance of NDE.
Good short-term memory seems to be essential for remembering NDE.
Patients with memory defects after prolonged resuscitation reported fewer experiences than other patients in our study.
Forgetting or repressing such experiences in the first days after CPR was unlikely to have occurred in the remaining patients, because no relation was found between frequency of NDE and date of first interview.
However, at 2-year follow-up, two patients remembered a core NDE and two an NDE that consisted of only positive emotions that they had not reported shortly after CPR, presumably because of memory defects at that time. It is remarkable that people could recall their NDE almost exactly after 2 and 8 years.
Our finding that women have deeper experiences than men has been confirmed in two other studies,1,7 although in one,7 only in those cases in which women had an NDE resulting from disease.
Our findings show that the process of change after NDE tends to take several years to consolidate. Presumably, besides possible internal psychological processes, one reason for this has to do with society's negative response to NDE, which leads individuals to deny or suppress their experience for fear of rejection or ridicule.
Thus, social conditioning causes NDE to be traumatic, although in itself it is not a psychotraumatic experience. As a result, the effects of the experience can be delayed for years, and only gradually and with difficulty is an NDE accepted and integrated. Furthermore, the long-lasting transformational effects of an experience that lasts for only a few minutes of cardiac arrest is a surprising and unexpected finding.
Several theories have been proposed to explain NDE.
We did not show that psychological, neurophysiological, or physiological factors caused these experiences after cardiac arrest.
Neurophysiological processes must play some part in NDE. Similar experiences can be induced through electrical stimulation of the temporal lobe (and hence of the hippocampus) during neurosurgery for epilepsy,23 with high carbon dioxide levels (hypercarbia),24 and in decreased cerebral perfusion resulting in local cerebral hypoxia as in rapid acceleration during training of fighter pilots,25 or as in hyperventilation followed by valsalva manoeuvre.4
Ketamine-induced experiences resulting from blockage of the NMDA receptor,26 and the role of endorphin, serotonin, and enkephalin have also been mentioned,27 as have near-death-like experiences after the use of LSD,28 psilocarpine, and mescaline.21
These induced experiences can consist of unconsciousness, out-of-body experiences, and perception of light or flashes of recollection from the past.
These recollections, however, consist of fragmented and random memories unlike the panoramic life-review that can occur in NDE. Further, transformational processes with changing life-insight and disappearance of fear of death are rarely reported after induced experiences.
Thus, induced experiences are not identical to NDE, and so, besides age, an unknown mechanism causes NDE by stimulation of neurophysiological and neurohumoral processes at a subcellular level in the brain in only a few cases during a critical situation such as clinical death. These processes might also determine whether the experience reaches consciousness and can be recollected.
With lack of evidence for any other theories for NDE, the thus far assumed, but never proven, concept that consciousness and memories are localized in the brain should be discussed.
How could a clear consciousness outside one's body be experienced at the moment that the brain no longer functions during a period of clinical death with flat EEG?22
Also, in cardiac arrest the EEG usually becomes flat in most cases within about 10 s from onset of syncope.29,30 Furthermore, blind people have described veridical perception during out-of-body experiences at the time of this experience.31 NDE pushes at the limits of medical ideas about the range of human consciousness and the mind-brain relation.
Another theory holds that NDE might be a changing state of consciousness (transcendence), in which identity, cognition, and emotion function independently from the unconscious body, but retain the possibility of non-sensory perception.7,8,22,28,31
Lancet December 15, 2001; 358: 2039-45
The Lancet is one of the world's most respected medical journals. So when it published an article in its current edition in which scientists claim to have PROOF that humans have a life after death that exists independently of the body that it inhabits, folks are sitting up and taking notice.
Many readers of this newsletter have strong spiritual convictions about the existence of the soul, but it is wonderful to have medical science support these convictions.