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Hasler F , Grimberg U, Benz MA, Huber T, Vollenweider FX. 
“Acute psychological and physiological effects of psilocybin in healthy humans: a double-blind, placebo-controlled dose-effect study”. 
Psychopharmacology. 2004 March;172(2):145-156.

RATIONALE: Serotonin 5-Hydroxytryptamine, 5-HT receptors play an important role in perception, affect regulation and attention. Pharmacological challenge with the 5-HT2A agonist psilocybin PY is useful in studying the neurobiological basis of cognition and consciousness.

Investigation of dose-dependent effects of PY on psychopathological and physiological parameters. Methods Eight subjects received placebo PL, and 45 very low dose, VLD, 115 low dose, LD, 215 medium dose, MD, and 315 high dose, HD g/kg body weight PY. The Altered States of Consciousness Rating Scale 5D-ASC, the Frankfurt Attention Inventory FAIR, and the Adjective Mood Rating Scale AMRS were used to assess the effects of PY on psychopathological core dimensions, attention, and mood. A 24-h electrocardiogram EKG was recorded and blood pressure was measured. Plasma concentrations of thyroid-stimulating hormone TSH, prolactin PRL, cortisol CORT, adrenocorticotropic hormone ACTH, and standard clinical chemical parameters were determined. Results PY dose dependently increased scores of all 5D-ASC core dimensions. Only one subject reacted with transient anxiety to HD PY. Compared with PL, MD and HD PY led to a 50 reduction of performance in the FAIR test. General inactivation, emotional excitability, and dreaminess were the only domains of the AMRS showing increased scores following MD and HD PY. The mean arterial blood pressure MAP was moderately elevated only 60 min following administration of HD PY. Neither EKG nor body temperature was affected by any dose of PY. TSH, ACTH, and CORT plasma levels were elevated during peak effects of HD PY, whereas PRL plasma levels were increased following MD and HD PY.

CONCLUSIONS: PY affects core dimensions of altered states of consciousness and physiological parameters in a dose-dependent manner. Our study provided no cause for concern that PY is hazardous with respect to somatic health.

Keywords Psilocybin - Dose-effect study - Psychopathology - Neuroendocrinology - Cardiovascular effects - Altered states of consciousness
Notes # : First Published Online Nov 13 2003 Heffter Research Center, Psychiatric University Hospital Zurich, Lenggstrasse 31, 8029 Zurich, Switzerland DOI: 10.1007/s00213-003-1640-6
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