Hallucinogen Persisting Perception Disorder

Hallucinogen persisting perception disorder, usually abbreviated HPPD, is a non-psychotic condition in which a person continues to experience lasting or recurring visual hallucinations or perceptual distortions after having used a hallucinogenic drug such as a psychedelic, a dissociative, a deliriant, an entactogen or a cannabinoid. Its symptoms can include visual snow, trailing images and afterimages, geometric light patterns seen on flat surfaces, intensified colors, altered perception of motion, pareidolia, and objects appearing smaller or larger than they are. A diagnosis requires ruling out other psychological, psychiatric and neurological conditions and confirming that the visual changes cause real distress in daily life; the disorder is divided into two types, with the more drastic HPPD II believed to involve associated mental disorders as well as hallucinogen use. It is rarely recognized by either hallucinogen users or psychiatrists and is distinguished from a hallucinogen-induced psychotic disorder by involving lasting visual changes alone, without paranoia, insomnia, altered thinking or delusions. The underlying mechanism is not well understood, though one hypothesis holds that anxiety can amplify existing visual disturbances, since many who experience the condition report their visual distortions growing more pronounced during periods of heightened anxiety or stress.