Harris Isbell of the National Institute of Mental Health reports in Psychopharmacologia on the physiological changes and mental states of 9 people given 57 to 114 mcg/kg of psilocybin, 1.0 to 1.5 mcg/kg of LSD, and a placebo. The test subjects were all “…negro males who were former drug addicts and who were serving for violation of the United States narcotic laws.” Psilocybin and LSD both caused increases in pulse, respiratory rates, temperature, and pulse. The effects of LSD lasted longer than those of psilocybin and Isbell concluded that LSD is 100-150 times more potent than psilocybin. Subjects experienced feelings of “strangeness” anxiety, altered sensory perception (mostly visual), difficulty thinking, elementary and true visual hallucinations, and altered body image.