Derek K. Tracy, Oxleas NHS Foundation Trust, Green Parks House, Kent, UK.
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 Hedgehog antagonist proposed. Inhibitors,research,lifescience,medical 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 Inhibitors,research,lifescience,medical 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, Inhibitors,research,lifescience,medical 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 Inhibitors,research,lifescience,medical 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. It is important to note that in contrast to classical psychotic disorders,

patients with HPPD recognize the unreal nature of their visual disturbances which Inhibitors,research,lifescience,medical qualifies them as pseudohallucinations. Method A MEDLINE literature search (1994–2011) with the keywords ‘Hallucinogen persisting perception disorder HPPD’ was conducted. Case report History The female patient, now 33 years Bumetanide old and an architect by profession, reported the recreational use of up to 30 doses of lysergic acid diethylamide (LSD; ‘tabs’) during a 1-year stay in the USA at the age of 18. Each single dose was probably limited to 100 µg and consumed in a peer group setting. She also used marijuana for relaxation and occasionally experimented with ecstasy, psilocybin mushrooms and ketamine. Approximately 2–3 weeks after returning to Europe, and the last drug taking, the patient developed persistent visual disturbances from which she has been suffering ever since.