PNAS nexus
April 1, 2025
Katie Zhou, David de Wied, Robin L Carhart-Harris et al.
9 citations
Delusional ideation decreased one month after a planned psychedelic experience, while magical thinking showed no change. Over 30% of participants reported hallucinogen persisting perception disorder (HPPD)-type effects at four weeks, though fewer than 1% found them distressing. Younger age, female gender, a history of psychiatric diagnosis, and baseline trait absorption predicted HPPD-like effects. Lifetime psychedelic use at baseline correlated positively with both magical thinking and delusional ideation, suggesting these traits may correlate with psychedelic use rather than being caused by it.
November 15, 2022
Katie Zhou, D. de Wied, Robin Carhart‐Harris et al.
8 citations
preprint
About a third (32.7%) of people reported symptoms of hallucinogen persisting perception disorder (HPPD) four weeks after a real-world psychedelic experience, but only 2.94% found those symptoms distressing. Delusional ideation was slightly higher among those with more lifetime psychedelic use at baseline, yet it decreased significantly four weeks after the experience, suggesting the baseline correlation may not be causal. Younger age, female gender, a personality trait called absorption, less non-psychedelic substance use in the prior six months, and using psychedelics outside a retreat setting predicted HPPD-like symptoms. The findings are limited by the observational design.
bioRxiv Preprint Server
May 1, 2025
Claudio Agnorelli, Joseph Peill, Gabriela Sawicka et al.
preprint
A single psychedelic dose of ketamine (1 mg/kg, intravenous) alters brain chemistry and connectivity in healthy people for at least one to eight days. After the dose, glutamate levels in the anterior cingulate cortex rose significantly. Functional connectivity decreased within high-order networks such as the default mode network, while integration between low- and high-order networks increased. Increases in a PET marker of synaptic plasticity correlated with reduced intrinsic activity in default mode network regions and a diminished influence of the posterior cingulate cortex on global network dynamics. The posterior cingulate cortex appears to be a central hub through which ketamine may reshape brain hierarchies over the long term.