The psychedelic drug psilocybin, a naturally occurring compound found in some mushrooms, has been studied as a potential treatment for depression for years. But exactly how it works in the brain and how long beneficial results might last is still unclear. In a new study, Yale researchers show that a single dose of psilocybin given to mice prompted an immediate and long-lasting increase in connections between neurons. The findings were published on July 5, 2021 in the journal Neuron. The article is titled “Psilocybin Induces Rapid and Persistent Growth of Dendritic Spines in Frontal Cortex In Vivo.” "We not only saw a 10% increase in the number of neuronal connections, but also they were on average about 10% larger, so the connections were stronger as well," said Yale's Alex Kwan, PhD, Associate Professor of Psychiatry and of Neuroscience and senior author of the paper.