In this dissertation; the history of the use of psychedelic substances, the studies concerning these substances, the methodologies and results of these studies, the future of the potential use of psychedelic substances, and the obstacles that scientists faced in their quest to find these uses will be written about in detail; analyzing all the available data in order to deal with the important and controversial question; "can psychedelic drugs be of therapeutical -or otherwise- importance in the field of psychiatry, and if so, how?"