Depersonalization-derealization syndrome

In this condition, the individual loses a sense of relationship with his own personality; the world becomes unreal and he is a stranger to himself. He imagines that the face he sees in the mirror has changed, it seems to be the face of someone else; his voice is not his own, his thoughts are bizarre, his actions are automatic. He may feel he has no body, that he is not real, that he does not even exist, or is a shadow or ghost.

Schizophrenia and serious memory disturbances, are frequently accompanied by symptoms of depersonalization. Mental patients are said to be estranged from themselves. Persons with certain nervous diseases, like allochiry (lacking self-perception of one half of the body), often suffer from a sense of partial or total depersonalization. Their limbs are not real limbs, or not their own limbs; their familiar surroundings become unreal; well-known faces assume a strange unreality and become unrecognizable. It can also result from long periods of insomnolence or sensory deprivation; can come as a result of epilepsy, hysteria, migraine, extreme torture or extreme pain, great emotional stress; psychedelic drugs can induce it as well, and ecstasy and visionary experience may result in temporary depersonalization.