Psychic decoherence

Psychic decoherence is when parcels of one's atman become frayed or destroyed by the imperfect process of death and reincarnation. Over time, atmans who decohere resemble their originals less and less, as memory gaps are bridged with fabrications, until an enduring sense of the unreal pervades everything they know. Revenants are atmans who suffer so much psychic decoherence they become unrecognizable from their original self, and often aggressive.

Symptoms
Decoherence may cause delusions and hallucinations parallel to apparent schizophrenia, convulsions, limited intelligence, inexplicable homicidal urges, panic disorders, hierarchical and antisocial tendencies to manipulate, 'insatiable' pica, memory loss, psychopathology, excessive detachment or dissociation, and/or survival complex personality disorders.

Causes of Decoherence
Despite religious theories and conjecture, no concrete explanation for decoherence currently exists. The most universally accepted is that deaths, and the psychological trauma and computational errors that they bring, cause decoherence.

The modern consensus of amnesians is that poorly kept phylacteries cause decoherence by randomly destroying or corrupting aspects of the atman. The atman itself responds by fabricating new memories and connections. When an atman has destroyed itself to the point where the atman consciously suffers for the process, it is considered decoherence.

Flawless Phylacteries
There are no phylacteries which are considered officially perfect beyond a doubt, and never cause decoherence in an atman. Some are worse than others.

Phylacteries where reincarnation occurs without any apparent evidence of decoherence are rare in the extreme, and sought after. Worlds in possession of so called "flawless phylacteries" often do not reveal themselves as such. In the case of the Ghintish Phylactery, several resurrected world leaders claim death has purified their atman - leading many to question their judgement.

Decoherence is widely believed to be irreversible, but discredited amnesians and psychotherapists state otherwise.