An altered state of consciousness can come about accidentally through indigestion, fever, sleep deprivation, starvation, oxygen deprivation, nitrogen narcosis (deep diving, or a traumatic accident. It can sometimes be reached intentionally by the use of a sensory deprivation tank or mind-control techniques, hypnosis, meditation, prayer, or disciplines e g Mantra Meditation, Yoga, Sufism or Surat Shabda Yoga ,.
