Dr. Torsten Passie (born 1961) is a German psychiatrist and internationally known scientific expert on altered states of consciousness. He is a Professor of Psychiatry and Psychotherapy at Hannover Medical School and Visiting Professor of Psychiatry at Harvard Medical School. He studied philosophy and sociology (MA) at Leibniz University Hannover and medicine at Hannover Medical School. He worked at the Psychiatric University Clinic in Zurich and with Professor Hanscarl Leuner (Gottingen), the leading European authority on hallucinogenic drugs. He has investigated altered states associated with breathwork, nitrous oxide, cannabis, ketamine, LSD, MDMA, and psilocybin. He has studied psychedelic microdosing, LSD-assisted psychotherapy for terminal illness, psychedelic treatment for PTSD, psychopharmaceutical and sociopolitical histories of MDMA use, LSD analogs/lysergamides, and effects of subanesthetic doses of ketamine. He has authored several books including 'Healing with Entactogens' (2012/2017), 'The Pharmacology of LSD' (2010), and 'The Science of Microdosing Psychedelics' (2019), and has published over 100 peer-reviewed papers on psychedelic pharmacology. He is currently also a visiting scientist at Goethe University Frankfurt/Main.