Hallucinogen Persisting Perception Disorder (HPPD) is a cognitive disorder in which individuals continuously re-experience visual and other hallucinations first experienced while intoxicated. The persistent nature of the hallucinations – flashes of color, for example, or halos around objects, or objects that appear too big or too small – and the fact that they occur while the individual is sober are indications of the presence of HPPD.
HPPD is divided into two types, according to the kinds of hallucinations the person experiences. In Type 1, an individual experiences brief, random flashbacks. In Type 2, the experience is more disturbing and persistent and an individual may experience consistent changes in vision
It is important to note that HPPD hallucinations are always obvious as hallucinations to the individual experiencing them and don’t override their reality. Despite that, HPPD can still cause significant distress and interfere with one’s work and social life.