A systematic review of 20 studies with 2,959 participants found that psilocybin's effects on cognitive function are mixed. Global cognitive function and processing speed remained mostly unchanged in healthy individuals, while improvements in sustained attention, working memory, and executive function were reported in patients with treatment-resistant depression. Emotional processing and empathy were positively modified, especially in these patients, but cognitive empathy and social cognition were not significantly altered. Cognitive flexibility and creative cognition initially declined but could improve over time. Psilocybin improved semantic associations and associative learning, but effects on episodic and verbal memory were less pronounced than with other cognitive enhancers.
In a pair of identical twins where one had obsessive-compulsive disorder and the other did not, the affected twin self-administered low, non-psychedelic doses of psilocybin. After the regimen, the affected twin reported a notable reduction in OCD symptoms, improved emotional regulation, and greater well-being. However, cognitive flexibility deficits—the ability to shift thinking—remained compared to the unaffected twin. This suggests that microdosing psilocybin may help relieve some OCD symptoms but does not fully address underlying cognitive impairments. Larger, longer studies are needed to understand how these low doses work and their potential as a treatment.