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Hallucinogen persisting perception disorder is a non-psychotic disorder in which a person experiences apparent lasting or persistent visual hallucinations or perceptual distortions after a previous hallucinogenic drug experience. This disorder usually resolves in a few weeks to several months, though more severe cases have reported life-long and greatly impairing symptoms. The hallucinations and perceptual changes consist of but are not limited to visual snow, trails and after images , light fractals on flat surfaces, intensified colors, altered motion perception, pareidolia, micropsia, and macropsia. People who have never previously taken drugs have also reported some visual anomalies associated with HPPD.
HPPD is a DSM-5 diagnosis with diagnostic code 292.89. For the diagnosis to be made, other psychological, psychiatric, or neurological conditions must be ruled out and it must cause distress in everyday life. In the ICD-10, the diagnosis code F16.7 corresponds most closely to the clinical picture. HPPD is little known among both hallucinogen users and psychiatrists and is often misdiagnosed as a substance-induced psychosis.
Despite HPPD being rare, many cases are temporary, resolving without the need for medication or other such treatments. However, newer research makes a distinction between HPPD I and HPPD II. The more drastic cases, as seen in HPPD II, are believed to be caused by abuse of psychedelics as well as comorbid mental disorders. Some people who have this disorder report that they developed symptoms of HPPD after their first use of such drugs. Due to the nature of HPPD being exceedingly misunderstood and under researched, few of these claims/experiences have been properly validated by the scientific community.