Hallucinogen persisting perception disorder (HPPD) is a disorder characterized by a continual presence of sensory disturbances, most commonly visual, that are reminiscent of those generated by the use of hallucinogenic substances. Previous use of hallucinogens by the person is necessary, but not sufficient, for diagnosis of HPPD. For an individual to be diagnosed with HPPD, the symptoms cannot be due to another medical condition. HPPD is distinct from flashbacks by reason of its relative permanence; while flashbacks are transient, HPPD is persistent. HPPD is a DSM-IV diagnosis with diagnostic code 292.89.
The complex phenomenology of acute hallucinogen-induced psychosis has been described and analysed extensively over the years. However, the clinical relevance of the long-term psychological sequelae which include so-called flashbacks remains unclear [Hermle et al. 1992; Hermle et al. 2008]. Moreover, a consistent etiological model to explain these effects has yet to be proposed. Ever since the first description [Cooper, 1955], reports about the incidence of post-toxic flashbacks show a wide variation. Between 5% and 50% of hallucinogen users are reported to have experienced at least one flashback [Alarcon et al. 1982; McGee, 1984].
Flashbacks, echo phenomena and other psychotic manifestations typically occur after drug-free periods of varying lengths. In the International Classification of Diseases, 10th revision (ICD-10), such hallucinogen-induced echo psychoses are listed under F16.70 [Dilling et al. 1991; Pechnik and Ungerleider, 2004]. However, the Diagnostic and Statistical Manual of Mental Disorders, fourth revised edition (DSM-IV-R) [American Psychiatric Association, 1994], classifies these phenomena under the term ‘hallucinogen persisting perception disorder (HPPD)’ – defined as a long-lasting condition characterized by spontaneous recurrence of visual disturbances reminiscent of acute hallucinogen intoxication. Such experiences may take the form of various geometric shapes, objects in the peripheral visual fields, flashes of different colours, enhanced colour intensity, trailing and stroboscopic perception of moving objects, after images, halos and macro- and micropsia. Furthermore, these episodes may persist for years. At variance with DSM-IV-R, ICD-10 recognizes hallucinogen-induced visual disturbances as lasting only seconds to minutes.
HPPD as defined in DSM-IV-R is a post- hallucinogen intoxication disorder encompassing a range of mostly visual perceptual disturbances that occur within a certain time frame after cessation of drug use. The definition of this disease entity is entirely based on studies involving chronic LSD users [Abraham, 1982, 1983]. However, any additional psychopathological symptoms that may have occurred in this patient population were not given any consideration. Pharmacotherapy of this very distressing condition is limited and any recommendations are based almost entirely on uncontrolled studies on small patient populations or even single case observations. Thus far, SSRIs, benzodiazepines, risperidone, olanzapine and naltrexone have all been tried with sometimes contradictory outcomes
It is important to note that in contrast to classical psychotic disorders, patients with HPPD recognize the unreal nature of their visual disturbances which qualifies them as pseudohallucinations.
People can develop HPPD after only 1 use of a hallucinogenic substance.
HPPD is most typically caused by the use of LSD.
About 1 in 50,000 hallucinogen users develop HPPD.
About 59% of people with HPPD see geometric patterns on blank surfaces like walls. Almost as many, see
false movements of still objects, usually in the peripheral visual fields. Others reports flashes of light, trailing images behind moving objects, intensified colors, and afterimagery.
Most people with HPPD recover within a month or two after last use, a few take as long as a year.
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