[adrice727]

  The present study focused on changes in brain function before versus after psilocybin in 
  patients with treatment-resistant depression who received two doses of the drug 
  (10 mg followed by 25 mg, one-week apart) as part of an open-label clinical trial.

25mg of pure psilocybin, the equivalent of 3.3 - 5 grams of dried mushrooms (depending on strength), is certainly enough for a trip.

[pizza]

It would be interesting to see if pure psilocybin (or prodrugs thereof) elicited as similarly-successful a response. I wonder to what extent other alkaloids, that are also present in mushrooms, affect the after-effects crucial to anti-depression.