- hallucinogen-induced persistent perception disorder
- (HPPD)Also known as hallucinogen persistent perception disorder and hallucinogen persisting perception disorder. All three names refer to a diagnostic category characterized by a recurrence or persistence of *entoptic phenomena and/or *visual hallucinations, reminiscent of those experienced during a prior episode of intoxication with a * hallucinogen. The American psychophar-macologist Henry David Abraham envisages HPPD as a perseverance of visual information, or a disinhibition of visual information processing, which may result in the occurrence of *afterimages, * trailing phenomena, * photopsia, and the formation of complex imagery on otherwise blank surfaces. Other symptoms of HPPD include * halos perceived around objects, transient *colour vision deficiencies, *visual snow, * metamorphopsias, and * muscae volitantes. Eti-ologically, HPPD is associated primarily with the prior use of a hallucinogen, but the syndrome has also been reported in individuals unaware of any such use. As to the pathophysiology of HPPD, quantitative EEG analyses (qEEGs) indicate that HPPD may be associated with a shortened occipital evoked potential latency. The prognosis of HPPD is variable. In some individuals the symptoms are self-limiting within a relatively short time span, while in others they may last for years. It has been suggested that in a conceptual and phenomenological sense (and perhaps a pathophysiological sense as well) HPPD is related to other mnestic events, such as drug-related * flashbacks, * post-traumatic flashbacks, *palinopsia, *phantompain, * reperceptive hallucinations, *eidetic imagery, and *flashbulb memories.ReferencesAbraham, H.D. (1983). Visual phenomenology of the LSD flashback. Archives of General Psychiatry, 40, 884-889.ffytche, D.H. (2007). Visual hallucinatory syndromes: Past, present, and future. Dialogues in Clinical Neuroscience, 9, 173-189.
Dictionary of Hallucinations. J.D. Blom. 2010.