Safety of Psilocybin in Clinical Setting
"Our investigations provided no cause for concern that administration of PY [psilocybin] to healthy subjects is hazardous with respect to somatic health. However, as our data revealed tendencies of PY to temporarily increase blood pressure, we advise subjects suffering from cardiovascular conditions, especially untreated hypertension, to abstain from using PY or PY-containing mushrooms. Furthermore, our results indicate that PY-induced ASC [altered states of consciousness] are generally well tolerated and integrated by healthy subjects. However, a controlled clinical setting is needful, since also mentally stable personalities may, following ingestion of higher doses of PY, transiently experience anxiety as a consequence of loosening of ego-boundaries."
Hasler, Felix; Grimberg, Ulrike; Benz , Marco A.; Huber, Theo; and Vollenweider, Franz, "Acute psychological and physiological effects of psilocybin in healthy humans: a double-blind, placebo-controlled dose–effect study," Psychopharmacology (Heidelberg, Germany: March 2004) Volume 172, Number 2, p. 151.