FEATURE PERSPECTIVE Getting Comfortable With Near Death Experiences An Overview of Near-Death Experiences by Bruce Greyson, MD An analysis of the incidence of NDEs among critically ill patients as documented in nine prospective studies in four countries yielded an average estimate of 17%. ear-death experiences transcending the ordinary confines (NDEs), profound of time and space. Although these experiences reported by events had been identified as a discrete Nsome people who survive close brushes syndrome as early as 1892,1 it was not with death, are important to clinicians until 1975 that Moody introduced the because they often lead to pervasive term near-death experiences (NDEs) for changes in attitudes and behavior; these phenomena. Moody described because they may be confused with characteristic features commonly psychopathological states; and because reported by survivors, including they may enhance our understanding ineffability, overwhelming feelings of of consciousness. Proposed peace, seeing a tunnel, a sensation psychological and physiological of being out of the body, meeting explanations lack empirical support nonphysical beings including a “Being and fail to explain NDEs, which pose of Light,” reviewing one’s life, a border a challenge to current models of the or point of no return, and coming back mind-brain relationship. to life with marked changes in attitudes and with knowledge not acquired Introduction through normal perception.2 A recent When some people come close review of the accumulated findings Bruce Greyson, MD is the Chester F. Carlson Professor of Psychiatry & Neurobehavioral to death, they go through a profound from thirty years of research since Sciences and Director of the Division of experience that may include a sense Moody’s seminal work has essentially Perceptual Studies at the University of 3 Virginia School of Medicine. of leaving the body and entering confirmed his original description. Contact: [email protected] some other realm or dimension, An analysis of the incidence Missouri Medicine | November/December 2013 | 110:6 | 471 FEATURE PERSPECTIVE One of the problems with NDE research, is that almost all of it has been retrospective, raising the question of reliablity of the experiencer’s memories. of NDEs among critically ill patients as documented in in age, gender, race, religion, religiosity, mental health, nine prospective studies in four countries yielded intelligence, neuroticism, extroversion, trait and state an average estimate of 17%.3 With advancements anxiety, or relevant Rorschach measures.11 in medical resuscitation techniques, the frequency of NDEs has increased, and thus about 9 million Expectancy people in the United States alone have reported A plausible hypothesis postulates that near- this kind of experience.4 In the last 30 years, the death experiences are products of the imagination, near-death phenomenon has been investigated constructed from one’s personal and cultural extensively.5 Near-death experiences are important to expectations, to protect oneself from facing the physicians for three reasons. First, NDE precipitate threat of death. Comparisons of NDE accounts pervasive and durable changes in beliefs, attitudes, from different cultures suggest that prior beliefs and values.6 Second, they may be confused with have some influence on the kind of experience a psychopathological states, yet have profoundly person will report following a close brush with different sequelae requiring different therapeutic death. approaches.7 Third, clarification of their mechanisms However, individuals often report experiences may enhance our understanding of consciousness and that conflict with their specific religious and its relation to brain function.8 personal expectations of death; people who had no prior knowledge about NDEs describe the One of the problems with research into NDEs is same kinds of experiences as do people who are that, with a few notable exceptions, almost all NDE quite familiar with the phenomenon, and the research has been retrospective, raising the question knowledge individuals had about NDEs previously of the reliability of the experiencer’s memories. does not seem to influence the details of their own Autobiographical memories are subject to distortion experiences; experiences that were reported before over years, and memories of unusual or traumatic 1975, when Moody’s first book coined the term events may be particularly unreliable as a result of NDE and made it a well-known phenomenon, do emotional influences. However, memories of NDEs not differ from those that were reported since that are experienced as “more real” than memories of date;12 and young children, who are less likely to 9 other events, and memories of NDEs have been have developed expectations about death, report 10 shown to be unchanged over a period of 20 years. NDEs with features similar to those of adults. Cross-cultural differences in NDE accounts Explanatory Models suggest that it is not the core experience that differs Studies of near-death experiencers have shown but the ways in which people interpret what they them collectively to be psychologically healthy have experienced in terms of the images, concepts, individuals who do not differ from comparison groups and symbols available to them.13 472 | 110:6 | November/December 2013 | Missouri Medicine FEATURE PERSPECTIVE Birth Memories medications in fact report fewer NDEs than do patients Some authors have suggested that NDEs, with who receive no medication.14 their dark tunnel, bright light, and going to another Furthermore, organic brain malfunctions generally realm, could represent memories of one’s birth. produce clouded thinking, irritability, fear, belligerence, However, newborns lack the visual acuity, spatial and idiosyncratic visions, quite unlike the exceptionally stability of their visual images, mental alertness, clear thinking, peacefulness, calmness, and predictable and cortical coding capacity to register memories content that typify the NDE. Visions in patients with of the birth experience, and reports of out-of-body delirium are generally of living persons, whereas those experiences (OBEs) and passing through a tunnel to of patients with a clear sensorium as they approached another realm are equally common among persons death are almost invariably of deceased persons. Patients born by Caesarean section and those born by normal who were febrile or anoxic when near death report fewer vaginal delivery.14 NDEs and less elaborate experiences than do patients who remain drug-free and are neither febrile nor anoxic. That is, drug- or metabolically-induced delirium, rather Altered Blood Gases than causing NDEs, in fact inhibits them from occurring A common assumption has been that anoxia or or being recalled.14 hypoxia, as a common final pathway to brain death, must be implicated in NDEs. However, NDEs Neurochemistry occur without anoxia or hypoxia, as in non-life- NDEs have been speculatively attributed to a threatening illnesses and near-accidents, and hypoxia number of neurotransmitters in the brain, most or anoxia generally produces idiosyncratic, frightening frequently endorphins or other endogenous opioids, a hallucinations, and leads to agitation and belligerence, putative ketamine-like endogenous neuroprotective agent quite unlike the peaceful NDE with consistent, universal acting on N-methyl-D-aspartate (NMDA) receptors, features. Furthermore, studies of people near death serotonin, adrenaline, vasopressin, and glutamate. These have shown that those who have NDEs have oxygen speculations are based on hypothetical endogenous levels the same as, or higher than, those who do not chemicals or effects that have not been shown to exist, have NDEs.15 Likewise, some authors have suggested and are not supported by any empirical data.17 that hypercarbia may contribute to NDEs; but several studies have reported carbon dioxide levels to be Neuroanatomy normal or below normal during NDEs.15 NDEs have also been speculatively linked to a number of anatomic locations in the brain, including the frontal lobe attention area, the parietal lobe orientation REM Intrusion area, the thalamus, the hypothalamus, the amygdala, the NDEs have been associated with intrusion into hippocampus, Reissner’s fiber in the central canal of waking consciousness of cognition typical of rapid eye the spinal cord, and most often the right temporal lobe, movement (REM) sleep. However, the REM intrusion based on purported similarity of NDEs to temporal lobe hypothesis is contradicted by the common occurrence seizure phenomena. However, NDE-like phenomena of NDEs under conditions that inhibit REM, such as are almost never seen in temporal lobe seizures, and 14 general anesthesia, and by the finding of reduced REM electrical stimulation of the temporal lobes typically in near-death experiencers.16 elicits fragmented bits of music, isolated and repetitive scenes that seemed familiar, hearing voices, experiencing Toxic or Metabolic Hallucinations fear or other negative emotions, or seeing bizarre, NDEs have been dismissed as elaborate dream-like imagery, in addition to a wide range of hallucinations produced either by medications given to somatic sensations that are never reported in NDEs.17 dying patients or by metabolic disturbances or brain These putative neurological mechanisms, for which malfunctions as a person approaches death. However, there is little if any empirical evidence, may suggest many NDEs are recounted by individuals who had brain pathways