The term tachypsychia comes from the Greek words tachos (swiftness) and psuchè (life breath, spirit, soul, mind). It translates loosely as ‘rapid mind’ or ‘fast psyche’. The term is used to denote an altered perception of time in which it is experienced as either speeded up or slowed down. Tachypsychia has been described chiefly under extreme circumstances such as physical exhaustion, extreme stress, and trauma. In addition, it has been described in the context of *aurae (as in paroxysmal neurological disorders such as migraine and epilepsy), and following the use of psychotomimetic substances such as LSD, cannabis, and mescaline. It has been suggested that the occurrence of tachypsychia is governed by the sudden release of neurotransmitters such as dopamine and catecholamines. Tachypsychia is classified as a specific type of dyschronation or *time distortion. When there is a significant increase in the speed of psychological time, the term *quick-motion phenomenon applies. A significant decrease in the speed of psychological time is called *protracted duration. See also the entry Slow-motion hallucination.