Researchers find the levels of psilocybin and psilocin in Psilocybe cubensis grown in controlled conditions increase with repeated harvests of the fruiting bodies. The amounts of the chemicals were generally zero in the first and sometimes second fruiting. The levels reach a maximum by the fourth fruiting with the level of psilocybin being at least 2X the level of psilocin. The researchers also tested the same mushroom species from outside sources and found the levels of psilocybin varied by over a factor of 10 from one batch to the next.