An out-of-body experience (OBE or sometimes OOBE) is a phenomenon in which a person perceives the world from a location outside their physical body. An OBE is a form of autoscopy (literally "seeing self"), although this term is more commonly used to refer to the pathological condition of seeing a second self, or doppelgänger.
The term out-of-body experience was introduced in 1943 by G. N. M. Tyrrell in his book Apparitions, and was adopted by researchers such as Celia Green, and Robert Monroe, as an alternative to belief-centric labels such as "astral projection" or "spirit walking". OBEs can be induced by traumatic brain injuries, sensory deprivation, near-death experiences, dissociative and psychedelic drugs, dehydration, sleep disorders, dreaming, and electrical stimulation of the brain, among other causes. It can also be deliberately induced by some. One in ten people has an OBE once, or more commonly, several times in their life.
Psychologists and neuroscientists regard OBEs as dissociative experiences occurring along different psychological and neurological factors.
Spontaneous OBEs
During/near sleep
Those experiencing OBEs sometimes report (among other types of immediate and spontaneous experience) a preceding and initiating lucid-dream state. In many cases, people who claim to have had an OBE report being on the verge of sleep, or being already asleep shortly before the experience. A large percentage of these cases refer to situations where the sleep was not particularly deep (due to illness, noises in other rooms, emotional stress, exhaustion from overworking, frequent re-awakening, etc.). In most of these cases subjects perceive themselves as being awake; about half of them note a feeling of sleep paralysis.
Near-death experiences
Another form of spontaneous OBE is the near-death experience (NDE). Some subjects report having had an OBE at times of severe physical trauma such as near-drownings or major surgery. Near-death experiences may include subjective impressions of being outside the physical body, sometimes visions of deceased relatives and religious figures, and transcendence of ego and spatiotemporal boundaries. The experience typically includes such factors as: a sense of being dead; a feeling of peace and painlessness; hearing of various non-physical sounds, an out-of-body experience; a tunnel experience (the sense of moving up or through a narrow passageway); encountering "beings of light" and a God-like figure or similar entities; being given a "life review", and a reluctance to return to life.
Resulting from extreme physical effort
Along the same lines as an NDE, extreme physical effort during activities such as high-altitude climbing and marathon running can induce OBEs. A sense of bilocation may be experienced, with both ground and air-based perspectives being experienced simultaneously.
Induced OBEs
Chemical
OBEs can be induced by hallucinogens (particularly dissociatives) such as psilocybin, ketamine, DMT, MDA, and LSD. These effects are believed to arise from interaction of these substances with a brain structure called the precuneus.
Mental induction
Falling asleep physically without losing awareness. The "Mind Awake, Body Asleep" state is widely suggested as a cause of OBEs, voluntary and otherwise. Thomas Edison used this state to tackle problems while working on his inventions. He would rest a silver dollar on his head while sitting with a metal bucket in a chair. As he drifted off, the coin would noisily fall into the bucket, restoring some of his alertness. OBE pioneer Sylvan Muldoon more simply used a forearm held perpendicular in bed as the falling object. Salvador Dalí was said to use a similar "paranoiac-critical" method to gain odd visions which inspired his paintings. Deliberately teetering between awake and asleep states is known to cause spontaneous trance episodes at the onset of sleep which are ultimately helpful when attempting to induce an OBE. By moving deeper and deeper into relaxation, one eventually encounters a "slipping" feeling if the mind is still alert. This slipping is reported to feel like leaving the physical body. Some consider progressive muscle relaxation as an active form of sensory deprivation. Deep trance, meditation and visualization. The types of visualizations vary; some common analogies include climbing a rope to "pull out" of one's body, floating out of one's body, getting shot out of a cannon, and other similar approaches. This technique is considered hard to use for people who cannot properly relax. One example of such a technique is the popular Golden Dawn "Body of Light" Technique.