Still Not Safe? What Scientists Don’t Know About Psychedelic Side Effects
Taking LSD or magic mushrooms may not be the cause of schizotypal traits.
Psychedelic drugs are experiencing a resurgence of interest in mainstream medicine, with early research indicating that psychedelic-assisted therapy may offer a safe and effective treatment option for certain mental health conditions. However, the full range of potential side effects remains insufficiently understood.
One area of concern is the possibility that psychedelics may trigger latent psychotic disorders or cause persistent perceptual disturbances. These disturbances are clinically recognized as Hallucinogen Persisting Perception Disorder (HPPD). To explore the prevalence and potential risk factors for such adverse effects, Katie Zhou and her research team conducted an online survey of 654 individuals who were independently planning to use psychedelics.
Among the original respondents, 315 participants completed a follow-up survey two weeks after their psychedelic experience, and 212 completed a second follow-up four weeks post-experience. The survey sample was predominantly male (74%) and highly educated, with 77% holding university degrees. Notably, approximately one-third of participants had a prior diagnosis of at least one psychiatric condition.
Correlation With Schizotypal Traits
The authors found a weak correlation between lifetime psychedelic use and both delusional ideation and magical thinking.
However, on average, delusional ideation was slightly reduced one month after psychedelic use. These results suggest that schizotypal traits may not be caused by taking LSD or magic mushrooms, in keeping with the principle that correlation does not imply causation.
About a third of individuals surveyed at the four-week mark did have some lingering hallucinatory sensory experiences, such as intensified colors and afterimages. However, the majority of those who experienced this did not report being distressed by it.
The strongest predictors of persistent visual aftereffects were the personality trait absorption—the tendency to be easily immersed in sensory or imaginative experiences—and younger age. This corroborates previous findings showing that young people and adolescents may be at a particular risk of HPPD. According to the authors, empirical scrutiny of the potential risks of psychedelics should accompany changes in policy and access to psychedelic drugs.
Reference: “Prediction of hallucinogen persisting perception disorder and thought disturbance symptoms following psychedelic use” by Katie Zhou, David de Wied, Robin L Carhart-Harris and Hannes Kettner, 22 April 2025, PNAS Nexus.