Rafael Guimarães dos Santos, Ph.D. In his M.Sc. in Psychology, he investigated the acute effects of ayahuasca on psychometric measures of anxiety, panic-like, and hopelessness in Santo Daime members. In his Ph.D. thesis in Pharmacology, directed by Dr. Jordi Riba, he compared the acute subjective and physiological effects of ayahuasca with those produced by d-amphetamine, and also investigated the pharmacology of two repeated doses of ayahuasca.