The latest episode of the Psychedelic Frontiers Podcast focuses on Hallucinogen Persisting Perception Disorder (HPPD) where individuals experience persistent visual hallucinations or perceptual distortions after previous use with drugs, including but not limited to psychedelics such as LSD. HPPD is rarely encountered in clinical settings, and its aetiology is poorly understood. Wide variations across participants are seen in symptoms, frequency and treatment-efficacy in this mysterious disorder, and it's clear more research is needed to identify its risk factors and underlying mechanisms. Today on the Psychedelic Frontiers Podcast, we’ll Torsten and Ben discuss what’s currently understood about HPPD, and review a recent systematic study exploring the disorder.

Dr Passie is a German psychiatrist, professor at Hannover Medical School and is an expert in altered states of consciousness and psychedelic substances. Torsten was part of the only systematic scientific investigation of more than 20 subjects claiming symptoms of HPPD, and the results have been published in a major neuroscience journal. He has also published the only comprehensive book on the subject of flashback phenomena such as HPPD as after-effects of hallucinogen ingestion, recreational or otherwise.

Ben Clayden, the creator and owner is currently studying for an MSci in Natural Sciences specialising in Neuroscience at the University of York. Alongside the podcast, he is the co-chair for Drug Sciences Student Society Network, as well as the president of his university's Drug Science Society. He has a key interest in and neuroimaging neuropsychopharmacology, particularly related to consciousness and mental health.

Halpern, J. H., Lerner, A. G., & Passie, T. (2018). A Review of Hallucinogen Persisting Perception Disorder (HPPD) and an Exploratory Study of Subjects Claiming Symptoms of HPPD. Current topics in behavioural neurosciences, 36, 333–360. https://doi.org/10.1007/7854_2016_457

Flashback-Phänomene als Nachwirkung von Halluzinogeneinnahme - Doris Holland, Torstan Passie, 2011 https://books.google.co.uk/books/about/Flashback_Ph%C3%A4nomene_als_Nachwirkung_von.html?id=t2cOMwEACAAJ

A thank you to Neel Radia, a member of the podcast team who helped with the research and script production for this episode

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