Near-death studies is a field of psychology and psychiatry that studies the physiology, phenomenology and after-effects of the near-death experience (NDE). The field was originally associated with a distinct group of North American researchers that followed up on the initial work of Raymond Moody, and who later established the International Association for Near-death Studies (IANDS) and the Journal of Near-Death Studies. Since then the field has expanded, and now includes contributions from a wide range of researchers and commentators worldwide. Research on near-death experiences is mainly limited to the disciplines of medicine, psychology and psychiatry. Near-death experience The near-death experience is an experience reported by people who have come close to dying in a medical or non-medical setting. The aspect of trauma, and physical crises, is also recognized as an indicator for the phenomenon. According to Linda J. Griffith and Bruce Greyson, it is estimated that near-death experiences are reported by five percent of the adult American population. According to IANDS, surveys (conducted in USA, Australia and Germany) suggest that 4 to 15% of the population have had NDEs. Researchers study the role of physiological, psychological and transcendental factors associated with the NDE. These dimensions are also the basis for the three major explanatory models for the NDE. Some general characteristics of an NDE include subjective impressions of being outside the physical body; visions of deceased relatives and religious figures; transcendence of ego and spatiotemporal boundaries. NDE researchers have also found that the NDE may not be a uniquely western experience. Commentators note that several elements and features of the NDE appears to be similar across cultures, but the details of the experience (figures, beings, scenery), and the interpretation of the experience, varies between cultures. However, a few researchers have "challenged the hypothesis that near-death experience accounts are substantially influenced by prevailing cultural models". Scientist correlate these events to a stressed and dying brain which affected the brain immensely therefore causing change. These visions and life changes could be caused by oxygen shortage, imperfect anesthesia and the body's neurochemical responses to trauma. But many NDErs still believe that they were more than just simple hallucinations or dreams. They believe these messages and the experience happened to them for a greater reason. Elements of the NDE According to the NDE-scale a near-death-experience includes a few, or several, of the following 16 elements: Time speeds up or slows down. Thought-processes speed up.