[Hallucinogen Persisting Perception Disorder (HPPD) and Flashback Phenomena – Differential Diagnosis and Explanation Models].

OBJECTIVE: The purpose of this article is to provide an overview of the current research on "Hallucinogen Persisting Perception Disorder" (HPPD) and "Flashback" phenomena. The definition and diagnostic features of "Flashback" and HPPD remained often unclear and since the 1960 s interchangeable.

METHODS: Relevant literature was identified by means of a computerized MEDLINE search including the years 1994-2014. Finally 75 journal articles out were included in the review.

RESULTS: Consistent with the ICD-10 (F16.70) definition "Flashback" is often used to describe brief visual perceptual, mood, and altered states of consciousness effects reminiscent of acute hallucinogen intoxication effects. Many users regard flashback phenomena as benign and even pleasant. HPPD is described in DSM-5 as a visual perceptual disorder, sometimes persisting for months or years causing severe individual distress. The prevalence of flashback and HPPD is unknown. It is considered to be remarkable in view of the relatively few case reports published out of millions of hallucinogen users since the 1960 s and 1970 s. Despite a multitude of etiological and therapeutic approaches the exact pathophysiological mechanisms underlying HPPD remain elusive. At present HPPD appears to be further a DSM-5-genuine but still puzzling disorder. The different consequences including new therapeutic approaches are discussed in clinical context.