A recent study found that about 33% of those who used psychedelics may have reported visual effects resembling hallucinogen persisting perception disorder 4 weeks following their experience, though less than 1% of them said those effects were distressing enough to meet clinical criteria for such health conditions.
Researchers followed 654 adult participants who were planning to use psychedelics such as lysergic acid diethylamide (LSD) or psilocybin in real-world, nonclinical settings. The participants were surveyed 1 week prior to, as well as 2 and 4 weeks following, their psychedelic use. Most of them used LSD (54%) or psilocybin (41%).
By the end of the study period, 32.1% of the participants reported at least one symptom associated with HPPD. The most common symptoms were seeing intensified colors (18.6%) and noticing lingering visual images, called “positive afterimages” (17.9%). Less common effects included distorted size perception, such as seeing things as unusually large or small.
Despite the number of participants reporting symptoms, only two participants found the effects distressing. Both of them had used psychedelics more than 10 times.
Lead study author Katie Zhou, of Imperial College London, and colleagues stated that: “2.9% of those who reported any HPPD-type effects expressed that these effects were distressing to them."
The researchers also found changes in thinking styles. Delusional thoughts, measured by a validated questionnaire, were significantly reduced following psychedelic use. This was true especially among the participants who had only used psychedelics a few times before. Magical thinking—beliefs in things like luck, superstition, or telepathy—didn't change significantly following the experience.
Notably, the participants who had used psychedelics more often in their lives had slightly higher scores for delusional and magical thinking prior to their most recent experience. But their scores didn’t worsen after using the drugs. Rather, overall, delusional thinking improved.
The researchers also looked at which participants were more likely to report HPPD-like symptoms. The risks were higher in younger participants, women, and those with a history of psychiatric conditions. Another strong predictor was “trait absorption”—a personality trait that describes being deeply immersed in thoughts, feelings, or imagination.
The researchers used several validated scales: the Peters’ Delusions Inventory (PDI) to measure delusional thinking, the Magical Ideation Scale (MIS), and the Modified Tellegen Absorption Scale (MODTAS). HPPD symptoms were measured with a custom nine-item checklist that included follow-up questions to determine whether symptoms were distressing or related to other conditions.
Most participants were young adults with a mean age of 28.9 years. The sample was mostly male (74.2%) and educated over 77% had at least a university degree. One-third of them had been diagnosed with a psychiatric disorder at some point.
While the researchers found that visual effects following psychedelic use may be relatively common, they emphasized that most individuals may not find them upsetting.
“The frequency of HPPD among psychedelic users overall would thus be estimated at < 1%, which is at least four times lower than the estimate provided by the DSM-V,” the study authors concluded.
The authors declare no competing interests.
Source: PNAS Nexus