Abnormal visual experiences in individuals with histories of hallucinogen use: A web-based questionnaire

This questionnaire-based study (n=2455) found that the risk of Hallucinogen Persisting Perception Disorder (HPPD) may increase with greater past exposure to specific hallucinogens, symptoms were rarely (4.2%) perceived as distressing/impairing.

Abstract

“Despite longstanding reports of prolonged or reoccurring perceptual changes in a subset of hallucinogen users, very little is known about Hallucinogen Persisting Perception Disorder and related visual abnormalities in hallucinogen users. We used an online questionnaire to document the symptoms and relationship to drug use of unusual visual phenomena in hallucinogen users. 16,192 individuals viewed the information sheet and 2679 were included in the study. Of these, 224 reported having unrelated diagnoses associated with unusual visual experiences and were excluded from main analyses. Most (60.6%) of the remaining 2455 participants reported having experienced drug-free visual experiences that resembled hallucinogen effects. Probability of experiencing constant or near-constant symptoms was predicted by greater past exposure to specific hallucinogens, including lysergic acid diethylamide (LSD). Although symptoms were common, few (104, or 4.2% of the sample) found them distressing or impairing enough to consider seeking treatment. Visual changes in hallucinogen users may be more common than previously suspected and are worthy of further study.”

Authors: M. J. Baggott, J. R. Coyle, E. Erowid, F. Erowid, L. C. Robertson

Summary

There have long been reports of prolonged or reoccurring visual abnormalities in hallucinogen users, but very few studies have examined the symptoms, prevalence, and relationship to drug use of hallucinogen persisting perception disorder.

The DSM-IV-TR states that HPPD includes any perceptual symptoms reminiscent of acute hallucinogen effects, but case reports rarely describe any hallucinogen-like effects except visual disturbances. HPPD symptoms may be intermittent or constant, and may occur on a daily basis for years.

Most studies providing estimates of visual changes in hallucinogen users predate the HPPD diagnosis, complicating interpretation. However, in a 10-year follow-up study of 247 individuals who received LSD as part of research or psychotherapy, five (2%) described “major perceptual changes”. Cohen (1960) collected information about hallucinogen-related complications from 44 investigators who had studied the effects of LSD or mescaline in 5000 individuals. He found that four subjects had experienced ‘fleeting afterimages’, but no cases had been reported for LSD.

Hallucinogen-experienced individuals were invited to complete a ‘visual experiences survey’ for 80 days. Anonymity was maintained by using an encrypted hypertext communication protocol and storing encrypted computer network (IP) addresses.

The survey asked participants about their drug-use history, past and present psychiatric and neurological diagnoses, and detailed information about their visual experiences. Participants were excluded from further analysis if they reported using a fictional drug called “kaopectamine”.

Four questions were asked to identify those with psychotic ideation, including whether they had ever been convinced that other people were watching them, thought they were in danger, or thought they had special powers. Respondents were asked about unusual visual experiences with the following question: “Halos or auras around things”, “Stationary things appear to move, breathe, grow, or shrink”), “Things that are moving appear to be not moving”), “Colors increase in brightness or intensity”, “Patterns”, “Things”), “Oscillations or flashing light sources”). Participants who endorsed any of the first seven listed visual experiences were asked about the frequency and phenomenology of these experiences, and whether these visual experiences had made social, work, school, or other activities so difficult that they considered getting professional treatment.

Data analysis focused on three main measures: number of unusual visual experiences endorsed (NUMSYMPT); number of constantly (or nearly constantly) occurring visual symptoms reported (NUMCONSTANT). Multiple logistic regressions were conducted using Poisson models to predict number of symptoms or binomial models to predict presence of symptoms.

2679 participants responded to the questionnaire, 85.3% met inclusion criteria, and 11.3% reported having at least one experience in addition to the nine experiences included in the questionnaire. There was a statistically significant relationship between self-reported visual exposures to individual drugs.

We made a Poisson regression to predict the number of constantly or nearly constant experiences (NUMCONSTANT) from log10 -transformed exposures to individual drugs. We found that constant symptoms increased the likelihood of seeking treatment, but only 12.9% of participants actually sought treatment.

Participants with HPPD reported sudden symptom onset, visual experiences, and paranoid ideation. Of these 45 HPPD-like participants, six reported non-drug events in the week before the experience, and 45 reported unusually high dose or strong effects, an acute dysphoric response to the drug, or first exposure to the specific drug.

33 otherwise-excluded individuals with a reported history of psychosis were examined regarding visual experiences. Those with psychosis were significantly less likely to report MOVEMENT and PATTERNS, and were more likely to endorse three of four questions designed to measure psychotic ideation.

We cannot determine the proportion of participants in whom these symptoms represent objective visual abnormality, but unusual drug-free visual experiences were strikingly common in our sample. 4.2% of participants indicated significant distress or impairment, and 1.7% reported abnormal visual symptoms without a clear temporal relationship to drug use.

We found that there were high numbers of people who experienced unusual visual experiences, particularly constant or near-constant experiences, and that there was a relationship between number of drug exposures and number of experiences. Several specific drugs were statistically associated with unusual visual experiences in our sample, with LSD being the most robust predictor. We collected data on reported temporal relationships between drug use and symptoms with sudden onset. LSD, psilocybin, high-dose DXM, and MDMA were most commonly associated with HPPD-like visual experience, although the relationship may have been coincidental in some cases.

HPPD-like experiences may be described in prodromal and first-episode psychosis, possibly relating to perceptual hypersensitivity and dysfunction in the magnocellular visual pathway. However, the majority of HPPD-like experiences in our sample argue against undiagnosed or prodromal psychosis.

This study relied entirely on self-report data from a convenience sample, and cannot diagnose any participants with HPPD or any other syndrome. However, given the limited knowledge of the frequency and character of HPPD in drug users, the results invite more research into this phenomenon. In conclusion, self-report data indicated that seemingly unusual drug-free visual experiences reminiscent of acute drug effects are common in hallucinogen users. More extensive use of LSD and several other hallucinogens significantly increased the probability of reporting unusual visual experiences.