What it is:
Hallucinogen Persisting Perception Disorder (HPPD) occurs in some individuals who have a history of using strong hallucinogens. Individuals who develop HPPD more than likely were users of lysergic acid diethylamide (LSD). Further, the amount of hallucinogens used does not affect the probability that one will acquire the disorder. In other words, some develop HPPD after using LSD several times, while others develop the same disorder after only one “trip” (Abraham, H.D., 2008).
The disorder is perceptual in nature and occurs when information received visually from one’s external environment is processed by the brain, but is unable to stop processing it. As a result, this visual information lingers in the form of “after-images”, flashes of light, trails behind moving images, and the development of complex imagery on surfaces where no imagery exists.
Research done by Drs. Abraham and Duffy (2008) has shown characteristic abnormalities in regards to electrical activity in the brains of HPPD patients. It is believed by some medical professionals that LSD, as well as other hallucinogens, destroy the inhibitory neurons that are responsible for the regulation and information sensory filtration. Others theorize that HPPD is a type of visual seizure comparable to epilepsy. Because HPPD is such a rare disorder, very little research has been done to investigate its causes (Hallucinogen Persisting Perception Disorder).
What it is not:
Many times, doctors misdiagnose HPPD patients as experiencing psychosis. On the contrary, HPPD patients usually do not experience psychosis, delusions, or auditory hallucinations- all symptoms of a psychotic illness. The research completed by Drs. Abraham and Duffy (2008) disproves any ideas of HPPD being a psychotic disorder, by showing the neurological differences between patients and nonpatients that are presented with visual stimuli.