> "Psilocybin, in 10mg or 25mg doses, has no short-term or long-term detrimental effects in healthy people... The research, published in The Journal of Psychopharmacology, is an essential first step in demonstrating the safety and feasibility of psilocybin – a psychedelic drug isolated from the Psilocybe mushroom – for use within controlled settings alongside talking therapy as a potential treatment for a range of mental health conditions, including treatment-resistant depression (TRD) and PTSD.'
Notice that very large doses were not studied, and the studies were conducted under controlled settings, with one-on-one support from a trained psychotherapist, in groups of up to six people simultaneously.
As the study was not flawed, then, under these conditions, psilocybin certainly seems like a safe and effective option for treatment.