Johannes studied medicine at the universities of Saarland/Germany, Rennes/France and Regensburg/Germany. He obtained his M.D. (Dr. med.) from the University of Saarland and worked as a clinical psychiatrist at the community hospital of Landsberg am Lech/Germany. In 2015 he joined the section of evidence-based medicine in psychiatry and psychotherapy at the Technical University of Munich/Germany. Since 2020 he is also an associate editor of the Cochrane Schizophrenia Group.