On Perception and Consciousness in HPPD: A Systematic Review
Pieter J. Vis, Anneke E. Goudriaan, Bastiaan C. Ter Meulen, Jan Dirk Blom
Frontiers in Neuroscience August 11, 2021 Peer reviewed DOI: 10.3389/fnins.2021.675768 via OpenAlex
Summary
Hallucinogen-persisting perception disorder (HPPD) is characterized by a range of perceptual symptoms, with 76% resembling Alice in Wonderland syndrome and over 50% being non-visual. Among 97 individuals studied, less than half experienced symptoms for over a year, but a third achieved remission. Those with co-occurring depression had longer-lasting symptoms and poorer treatment outcomes. The findings suggest that HPPD involves changes in consciousness distinct from acute psychedelic effects, indicating a need to expand its diagnostic criteria.
Study at a glance
| Design | systematic review |
|---|---|
| Sample size | 97 |
| Population | individuals with hallucinogen-persisting perception disorder (HPPD) |
| Key finding | HPPD encompasses a broader range of symptoms than suggested by the DSM-5, with significant implications for diagnosis and treatment. |
Abstract
Hallucinogen-persisting perception disorder (HPPD) features as a diagnostic category in the DSM-5, ICD-11, and other major classifications, but our knowledge of the phenomenology of the perceptual symptoms involved and the changes in consciousness during the characteristic “flashbacks” is limited. We systematically evaluated original case reports and case series on HPPD to define its phenomenology, associated (psycho)pathology, and course. Our search of PubMed and Embase yielded 66 relevant publications that described 97 people who, together, experienced 64 unique symptoms of HPPD. Of these, 76% concerned symptoms characteristic of Alice in Wonderland syndrome, over 50% non-visual symptoms, and 38% perceptual symptoms not clearly linked to prior intoxication states. This is in contrast with the DSM-5 diagnostic criteria for HPPD. Even though less than half of the patients showed a protracted disease course of over a year, a third achieved remission. However, in patients with co-occurring depression (with or without anxiety) HPPD symptoms persisted longer and treatment outcomes were more often negative. Thus, unlike the acute stages of psychedelic drug intoxication, which may be accompanied by altered states of consciousness, HPPD is rather characterized by changes in the content of consciousness and an attentional shift from exogenous to endogenous phenomena. Since HPPD is a more encompassing nosological entity than suggested in the DSM-5, we recommend expanding its diagnostic criteria. In addition, we make recommendations for clinical practice and future research.