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 colour, 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.

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The effects of taking larger doses of hallucinogens should wear off over the course of six to 15 hours. HPPD symptoms, however, persist long after the normal active life of the drug and can be either episodic or mostly continuous. These symptoms can last for weeks, months, and sometimes even years. In some cases the condition becomes chronic, while in other instances people can suppress the feelings and function normally.HPPD can occur in combination with other mental disorders, such as panic disorder, alcohol use disorder, and depression, according to the DSM-5, and some types of therapy used to teat those conditions may be helpful in managing HPPD symptoms as well.