Hallucinogen-persisting perception disorder (HPPD) involves perceptual symptoms and flashbacks after psychedelic use, but its phenomenology is poorly understood. A systematic review of 66 case reports and series covering 97 people identified 64 unique symptoms. Of these, 76% were characteristic of Alice in Wonderland syndrome, over 50% were non-visual, and 38% were not clearly linked to prior intoxication, contrasting with DSM-5 criteria. Fewer than half of patients had a protracted course over a year, and a third achieved remission. Co-occurring depression with or without anxiety was associated with longer symptom persistence and more negative treatment outcomes. HPPD involves changes in the content of consciousness and an attentional shift from external to internal phenomena, rather than the altered states seen in acute intoxication. The authors recommend expanding diagnostic criteria.
Hallucinogen persisting perception disorder (HPPD) involves lingering or recurring perceptual phenomena after substance use, which can be mild or severely burdensome. A systematic review of 31 medication studies covering 87 participants found that clonidine, clonazepam, and levetiracetam produced substantial symptom reduction in three observational studies. Among those receiving benzodiazepines, antiepileptics, antidepressants, or alpha agonists, 28% achieved full recovery and 61% partial recovery within a year. Benzodiazepines were ineffective when HPPD was triggered by lysergic acid diethylamide, and risperidone aggravated symptoms. The authors suggest these medications can treat HPPD effectively but call for randomized controlled trials and epidemiological studies.