Clarifying the mechanisms by which psychedelics achieve therapeutic efficacy

The potential psychotherapeutic value of psychedelic drugs has recently generated much scientific and public interest. Many comparative trials have suggested that these drugs can produce significant benefits for individuals suffering from various treatment-resistant psychological disorders. However, recent work in the philosophy of medicine has emphasized the importance of complementing evidence produced by comparative trials with “mechanistic evidence”. Mechanistic evidence is evidence that is produced by reasoning about the causal pathways (or mechanisms) by which treatments achieve their effects. It is important, therefore, to have a strong understanding of the mechanistic evidence for the therapeutic efficacy of psychedelics. This thesis seeks to strengthen the understanding of the mechanistic evidence for the therapeutic efficacy of psychedelics. By surveying past and contemporary proposals about how psychedelics produce benefit, I articulate two broad views that dominate contemporary understandings of the mechanistic evidence. According to “mind-manifesting” views, psychedelics are therapeutically useful because they facilitate access to unconscious content. On the other hand, according to “mind-modifying” views, psychedelics are therapeutically useful because they disrupt rigid thought patterns and increase psychological flexibility. I argue that these two views are sometimes conflated or not clearly distinguished by contemporary researchers, and that they need to be teased apart to generate a stronger understanding of exactly how psychedelics produce beneficial outcomes. I then explore the viability of using “psychedelic testimony” to help tease these views apart.Arts, Faculty ofPhilosophy, Department ofGraduat