How is psilocybin used to treat depression ?

How is psilocybin used to treat depression and how does it react in the brain with serotonin levels?

Psilocybin Treatment for Major Depression Effective for Up to a Year for Most Patients, Study Shows. Previous studies by Johns Hopkins Medicine researchers showed that psychedelic treatment with psilocybin relieved major depressive disorder symptoms in adults for up to a month.