The Buddhist literature and oral tradition record many instances of consciousness traveling with a subtle form outside the rough body. Such phenomena have also been noted in the West and often labeled as "astral body travel." Although it is difficult to correlate experiences and identify individual cases from one culture to another within the classification scheme of that other culture, nevertheless it may be useful to outline some varieties of this phenomenon as found in the Buddhist traditions of Indian and Tibet.
Through intensive, deep meditation practice, it is possible to achieve an illusory body (sgyu-lus). This is the result of extremely advanced complete stage (rdzogs-rim, completion stage) practice in the highest class of tantra, anuttarayoga. It is with this body that one gains the nonconceptual realization of voidness with a clear light subtlest mind. In this form, it is possible to travel extensively outside the limitations of one’s physical body, working for the benefit of others.
In order to attain an illusory body, it is necessary to have achieved beforehand renunciation of suffering, a bodhichitta aim to achieve Buddhahood in order to be able to help all others achieve the same, and a correct conceptual understanding of voidness. In addition, one must have attained single-pointed absorbed concentration (ting-nge-‘dzin, Skt. samadhi), received the proper tantric empowerments from a fully qualified tantric master, kept all the vows purely, and attained proficiency in the generation stage (bskyed-rim) and the initial complete stage practices of anuttarayoga tantra.
Through much meditation, one may also gain use of a dream body (rmi-lam-gyi lus). This form is particularly well suited for single-pointed attention, since while asleep one does not have the distraction of sense consciousness. Therefore, practitioners often cultivate it in order to make further progress in their studies. Having gained control over the dream state and mastered this type of emanation, one can set out books in one’s room and memorize them while asleep. However, as the dream body is unable to make contact with concrete objects and cannot turn pages, it is necessary to arrange several copies of the books so that there is no need for page turning.
Moreover, both dream and illusory bodies are connected to the rough body merely by karma. There are no physical links between the two.
Disturbances in the Subtle Body
What is known as the subtle body (lus phra-mo) is not a body that can leave one's gross physical form. Rather, it is the subtle energy system within one’s gross body. It is the network of invisible energy-channels (rtsa, Skt. nadi) and energy-nodes (rtsa-‘khor, Skt. chakra), the creative energy-drops (thig-le, Skt. bindu) located in them, and the energy-winds (rlung, Skt. prana) that flow through them. Parts of this system are involved in the normal functioning of sense perception. With absorbed concentration and advanced yogic training, it is possible to make special use of this system to gain extraphysical and extrasensory powers, such as telepathy and clairvoyance. However, there are also many sicknesses that result from disturbances and imbalances of the energy-winds. Such disorders may produce hallucinations and abnormal perception, such as the sensation of being outside one’s body.
Side Effects of Visualization Practices
In addition, there are many types of meditation in which one cultivates and harnesses the powers of imagination in order to make spiritual progress. For instance, by learning to visualize all beings as skeletons, one can lessen one’s compulsive attraction and craving for the body, and thus eliminate the suffering and anxiety of longing desire. One can train one's mind to visualize in all directions simultaneously and even to see the internal organs of the body. With mastery of such practices, it is possible to have such extended perception even outside one’s meditation sessions. Being able to see all around, one may feel as though one were beyond the limits of one’s own body.
Bodies of Mixed States of Existence
It is recorded that due to previous karma, one may be reborn as a half-human, half-ghost. Someone in that condition may find that when his human body is unconscious or in some way inactive, the spirit-like part of his nature will travel about together with his consciousness. There have also been cases known of people who were half-human, half-celestials (gods). Here a celestial spirit had taken a rough human body, but under certain conditions acted apart from this form. The above cases involve the consciousness of only one living being, who may have aspects, however, of two different states of existence.
Entering the Citadel of Another Body
It is also possible for an extra-bodily experience to involve more than one being. There are certain advanced anuttarayoga tantric meditation practices called "entering the citadel" of another body (grong-‘jug). With absorbed concentration, one can project one’s mind into the body of a fresh corpse or of someone who is unconscious. As this might easily be abused and undertaken for harmful purposes, the direct oral lineage of its practice was broken in the eleventh century before it could be brought from India to Tibet.
It is also possible for one’s own body or mind to be possessed by a being from the spirit realm. This may occur for beneficial reasons, as in the case of oracles in trance, or for harmful ones as with clutching ghosts (hungry ghosts). In the Buddhist literature, there is also mention of beings who have died and been reborn as spirits or hell-creatures and who have communicated from these states with their former relatives and friends. This is based on strong karmic connections, as is the recognition, for instance, of a donkey as having been one’s deceased uncle.
Extra-Bodily Experience Due to Previous Meditation Practice
No matter what type of extra-bodily phenomenon someone untrained in meditation might experience, it is the result of his or her previous actions of this or former lives. Different people have varying experiences, and even one individual will rarely experience the same thing twice. This is due to different karma and instincts from previous lives.
If formerly one has trained one’s mind with the advanced Buddhist meditations involving visualizations or the illusory, dream, or subtle bodies, one may be born with strong instincts for these practices. Then, without any effort, extra-bodily phenomenon may occur. In such instances, one would also have pronounced inclinations for the other meditations and insights in the context of which these advanced practices would have been undertaken. In other words, one would have instincts for the entire body of practice, not only for its advanced points. Thus from childhood one would also have had an intuitive feeling for cause and effect, rebirth, renunciation, compassion, voidness, and so forth. At least one would have an instinctive belief in past and future lives. For such people, it is worthwhile to find a fully qualified spiritual master and receive the proper meditation training to develop their potentials.
Extra-Bodily Experience Due to Maladies
If one does not have any inclination for the basic meditations, there may be other karmic causes for one’s extra-bodily experiences. Should one’s experience be preceded by a tight, anxious feeling in the solar plexus, rushes of energy from the heart to the head, a ringing or hissing in the ears, a clenching of the teeth, periods of unconsciousness and so forth, these may be indications of a disorder of the energy system of the subtle body. With such symptoms, it is not advisable to indulge in the abnormal states of perception that this type of disorder will produce. A serious imbalance of energy in the body, particularly when centered at the region of the heart, may lead to extreme paranoia, insanity, and even death. One should consult a Tibetan doctor for treatment.
It may be that harmful spirits or forces are causing one to have altered perceptions or to lose control of one’s consciousness. This is also a dangerous situation and should be handled by a lama, a physician, or an oracle who is expert in the rituals of exorcism. Should an extra-bodily sensation be the hallucination caused by a drug, this too should not be pursued. Long-lasting effects may occur from prolonged exposure to distortion of consciousness.
In summary, if, without meditation practice and specific training, one has an uncontrolled extra-bodily experience, one should not treat it lightly or as an amusing curiosity. The cause may be any of the above explanations, a combination of factors, or something else entirely. Regardless of the cause, should someone be startled while his or her consciousness is outside the physical body, it is very easy for the connection between the two to be severed. Buddhist literature records many cases of such deaths. Therefore, it is extremely important not to experiment on one’s own with extra-bodily states. However, with proper guidance, a good motivation, and intense meditation practice, such states may be harnessed to expand one’s potentials for helping others and oneself to the benefit of all.