Scientists are divided on what-if anything-might cause near-death experiences.
Believers in the supernatural and skeptical scientists seem to agree on only one thing: The near-death experience (NDE) is a remarkable phenomenon. But there's no consensus on what causes it, even among those who point to a range of possible biological factors that could trigger hallucinations.
Indeed, the research on both sides of the NDE debate leaves plenty of unanswered questions. For example, Dutch cardiologist Dr. Pim van Lommel, the researcher who reported in the British journal The Lancet
that 18 percent of 344 successfully resuscitated patients had had NDEs, concludes, "There is no apparent medical, physiological, pharmacological or psychological factor that causes the NDE. So the existing theories till now have to be abandoned." His research has been seized on by NDE advocates such as Dr. Barbara Rommer and other leaders in the International Association for Near-Death Studies
(IANDS) as the best evidence to date of the likelihood of an afterlife.
Yet van Lommel himself says, "I do not believe in an afterlife, but I believe that when the body has died, consciousness with memories will continue to be experienced, independent of the dead body." He points to theories of quantum physics-including the ever-shifting nature of matter and energy-as possibly explaining how awareness and memory could survive even when brain activity has ceased.
So what accounts for the full scope of the near-death experience? Usually, it involves a lucid awareness of strange events while a person is temporarily clinically dead - his heart, breathing and, in some cases, brain activity have stopped. The reported experiences include seeing one's own dead body, traveling through a tunnel, encountering a special light and deceased relatives, feeling peaceful emotions, having a life review or seeing celestial landscapes. Not all people who have NDEs recall all these features, but most are common elements of the experience.
Skeptical researchers contend that all these elements can be reproduced and explained through biological means. For instance, electrical stimulation of the temporal lobes of the brain can induce vivid memories and out-of-body experiences, and injection with the anesthetic ketamine (known to clubgoers as Special K) has been shown to create powerful hallucinations, including meetings with angelic figures. Another common explanation is that the deprivation of oxygen to the brain during a near fatality leads to neurological misfirings - and hallucinations.
"Since the brain can produce [the NDE] in a natural way, it makes pretty weak the case for the supernatural explanation," says James Alcock, a psychology professor at York University in Toronto and a leading skeptic.
But van Lommel and other researchers contend that the laboratory-induced hallucinations simply are too fragmented to match the NDE accounts. In addition, van Lommel's study, which tracked near-fatality survivors who'd had NDEs and those who hadn't for as long as eight years, argues that the profound sort of life changes among NDE patients don't take place in people who have induced hallucinations.
"People who have an experience with ketamine always say, `Oh God, did I have a horrible nightmare,'" Rommer adds. "They never think it's a real experience."
Van Lommel also claims that the medical explanations fall apart because only a minority of the people his team studied had NDEs, though all experienced approximately the same type of cardiac arrest. "If purely physiological factors.caused NDE, most of our patients should have had this experience," he wrote.
Still, skeptics, while not doubting the sincerity of NDE survivors, also note that human memory often embellishes experience or re-shapes it to fit personal beliefs. "Stories, on repetition, have a way of getting better and better," says Dr. Barry Beyerstein, a psychology professor at Simon Fraser University in British Columbia. He also cites "false-memory syndrome" and the often-changing accounts of eyewitnesses to crimes. "Where all you have is memory, be careful," he says.
Dr. Jeff Long, an IANDS board member, and other NDE researchers argue that NDE accounts are too consistent over time and often too inexplicable to be resolved so neatly. They even cite out-of-body visual details provided by blind people - some blind since birth - of hospital staff attending them. Similarly, van Lommel reported that a patient who was comatose during a cardiac arrest knew where the dentures removed from him were hidden. "How could a clear consciousness outside one's body be experienced . during a period of clinical death?" his study asked.