Hallucinogen persisting perception disorder

Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences lasting or persistent visual hallucinations or perceptual distortions after using drugs. This includes after psychedelics, dissociatives, entactogens, tetrahydrocannabinol (THC), and SSRIs. Despite being a hallucinogen-specific disorder, the specific contributory role of psychedelic drugs is unknown.

Symptoms may include visual snow, trails and after images (palinopsia), light fractals on flat surfaces, intensified colors, altered motion perception, pareidolia, micropsia, and macropsia. Floaters and visual snow may occur in other conditions.

For the diagnosis, other psychological, psychiatric, and neurological conditions must be ruled out and it must cause distress in everyday life. In the DSM-5 it is diagnostic code 292.89 (F16.983). In the ICD-10, the diagnosis code F16.7 corresponds most closely. It is rarely recognized by hallucinogen users and psychiatrists, and is often misdiagnosed as a substance-induced psychosis.

It is divided into two types HPPD I and HPPD II. The more drastic cases, as seen in HPPD II, are believed to be caused by the use of psychedelics as well as associated mental disorders. Some people report symptoms after their first use of drugs (most notably LSD). There is little information on effective treatments.

The underlying mechanisms is not well understood. One hypotheses suggests anxiety may amplify existing visual disturbances and potentially trigger these visual phenomena. Many report that their visual distortions become more pronounced or even emerge during periods of heightened anxiety or stress.