Visual Disturbances After Psychedelic Use
“It’s truly unclear whether this guy is at greater risk for psychosis,” Max Greenwald says, describing a 25-year-old man who contacted him after seeing a huge, unblinking eye in his ceiling every night as he fell asleep. The man had taken psychedelics in the past, prompting concerns about developing psychosis despite not having psychosis and not being on drugs.
The man’s experience highlights findings from a new study published in Scientific Reports by Greenwald and Albert Powers, medical director of Yale’s PRIME Psychosis Risk Clinic. The research examines persisting perceptual abnormalities, known as PPAs, which occur after psychedelic use and share features with early psychosis hallucinations.
High Rates of Perceptual Abnormalities in Psychedelic Users
Researchers recruited 186 psychedelic users largely through online forums to investigate changes in how the brain receives, interprets, and organizes information linked to substances like psilocybin and LSD. More than half of the participants reported experiencing PPAs following psychedelic use. Greenwald notes that while visual abnormalities have long been recognized as Hallucinogen Persisting Perception Disorder, clinical diagnoses remain rare because the condition requires clinically meaningful distress and impairment.
The study found a high frequency of PPAs because the researchers did not require participants to report distress. More than 90% of study participants reported no distress at all. Greenwald states that the most common side effect is simply seeing colors as brighter, which users do not necessarily find distressing. Participants who began using psychedelics at a younger age reported these visual effects at higher rates, suggesting that consumption during brain development increases the likelihood of persisting perceptual changes.
Parallels Between Psychedelic Side Effects and Prodromal Psychosis
Psychotic illness rarely begins abruptly. Albert Powers explains that an average of 22 months before a first psychotic episode, individuals often experience subtle sensory changes such as hearing buzzes, pops, or footsteps, or noticing brighter lights and louder sounds. Greenwald points out that these early symptoms of prodromal psychosis closely mirror the perceptual abnormalities that persist after psychedelic use.
However, determining whether a psychedelic triggers psychosis in vulnerable individuals remains difficult. Greenwald notes that when someone develops psychosis after taking a psychedelic, distinguishing whether the person would have developed the illness regardless—and the drug simply acted as a stress test—is complicated.
Psychedelic Users Experience Unexpected Conditioned Hallucinations in Sensory Test
To test how the brain processes sensory information, the research team utilized a task developed by Powers. Participants listened to a tone while faint stripes appeared in visual static, training the brain to associate the tone with the stripes. When the tone played later without the stripes, many participants saw them anyway due to conditioned expectations.
Researchers initially expected psychedelic users to show fewer conditioned hallucinations, operating on the theory that psychedelics loosen the brain’s reliance on expectations. Instead, participants with lingering effects saw more phantom stripes, felt more confident about them, and struggled to distinguish real stripes from static. The findings suggest a noisy visual system prone to random perceptual errors rather than an over-reliance on top-down expectations, pointing to an interplay between persistent visual noise and internal expectations.
Study Details Persistent Visual Changes and Participant Count
What specific visual abnormalities did participants report most frequently?
The study found that the most common persisting perceptual abnormality was simply seeing colors as brighter, with more than 90% of participants reporting no distress from these effects.
How many participants were included in the Yale School of Medicine study?
The research examined a sample of 186 psychedelic users, who were recruited largely through online forums.
What is prodromal psychosis?
Prodromal psychosis is the gradual onset of non-specific symptoms, such as difficulty focusing, irritability, and visual or auditory abnormalities, which typically precede a formal psychosis diagnosis by an average of about 22 months.
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