Hallucinogens as therapeutic agents: Past, Present and Future

Hallucinogens have a long history as therapeutic agents. After the synthesis of
lysergic acid diethylamide (LSD) in 1938 by Albert Hofmann, the popularity of
classical hallucinogens with psychedelic properties increased among scientists,
psychiatrists, neurologists, and psychotherapists. Research in the 1950s and
1960s showed great promise for the use of psychedelics in medical research
and treatment. Psychedelics are characterized by their mind revealing effects,
which are valuable in the treatment of major depressive disorder (MDD) and of
stress- and trauma-related mental disorders (PTSD). However, research into thetherapeutic uses of psychedelics became restricted, in part due to their classification
as drugs with abuse potential in the mid-1960s. In the past decade, psychedelic
research has been reestablished among several groups around the world
(Nutt, Erritzoe, and Carhart-Harris, Cell181 (1):24–28, 2020). There is growing
anticipation, awareness, and hope for the potential of these substances to become
medically approved as psychoactive treatments (Belouin and Henningfield, Neuropharmacology
142:7–19, 2018). In this chapter, we offer a historical overview
of psychedelic drugs and their uses and a discussion of chemical and pharmacological
properties, mechanisms of action, clinical studies, adverse effects, and
psychotherapeutic combination therapies with hallucinogens.