Hallucinogen persisting perception disorder (HPPD) is a disorder in which a person has flashbacks of visual hallucinations or distortions experienced during a previous hallucinogenic drug experience, sometimes with the same feelings experienced before, which cause distress or impairment in work or everyday life. The flashbacks may be continuous or just occasional.
HPPD is a DSM-5 diagnosis with diagnostic code 292.89 (F16.983). For the diagnosis to be made, other psychological, psychiatric, or neurological conditions must be ruled out.
The only certain cause for HPPD is prior use of hallucinogens. There are no known risk factors, and what might trigger any specific disturbing hallucination is not known. Some sort of disinhibition of visual processing may be involved.
As of 2018 there was no good evidence for any treatment. For people diagnosed with chronic HPPD, sunglasses and therapy might help. Antipsychotic drugs and SSRIs have been reported to help some people and worsen symptoms for others. Anticonvulsants and clonidine have also been tried.
The prevalence of HPPD was unknown as of 2018. Estimates in the 1960s and 1970s were around 1 in 20 for intermittent HPPD among regular users of hallucinogens. It is not clear if chronic HPPD exists, but one estimate in the 1990s was that 1 in 50,000 regular users might have chronic disturbing hallucinations.