Review of 32 placebo-controlled studies on how LSD, DMT and psilocybin affect thinking

The question

How do LSD, DMT and psilocybin affect mental abilities such as attention, memory, empathy and flexible thinking, both while the drug is active and afterwards?

What they did

The authors searched PubMed and APA PsycINFO (and additionally Google Scholar) between February 28 and March 19, 2025, for placebo-controlled studies published from 1990 to 2025. They looked for experimental studies measuring empathy, reaction time, attention, inhibition (the ability to hold back an automatic response), emotional processing, memory and cognitive flexibility (switching between ways of thinking). Thirty-two studies met their criteria and were summarized.

What they found

Across the 32 studies, psychedelics tended to increase emotional empathy (feeling what another person feels) but did not change cognitive empathy (working out what another person thinks). Effects on memory went in all directions: impaired, improved or unchanged, depending on the task and when it was measured. Many reaction time, attention and inhibition tasks showed impairments that grew with higher doses, though some studies found no effect. Some studies found people were less able to recognize negative emotional stimuli while the drug was active, and findings on cognitive flexibility were mixed.

The fine print

The review itself notes that many included studies had small samples and that a convincing placebo is hard to achieve, because people can usually tell when they have taken a psychedelic. Results were inconsistent across studies and tasks, and the abstract does not report a total number of participants or any pooled effect sizes. Most evidence concerns short-term effects, with little on longer-term change. This summary is based on the abstract only.

What it means

Classic psychedelics appear to shift some aspects of thinking and emotion in the short term, most consistently by slowing reaction-based tasks at higher doses and by increasing emotional empathy, but the overall picture is mixed and the underlying studies are small.

Evidence grade: Moderate. A systematic review of 32 placebo-controlled experimental studies, but the included studies were mostly small, results were mixed, and no pooled statistical analysis is reported in the abstract.

This summary is based on the study’s published abstract.