History of psychedelic drug science and molecular pharmacology.

Classic psychedelics have been used by various cultures for millennia for healing and religious purposes. The modern era of psychedelic science began with the first empirical experiments by Dr. Arthur Heffter in 1898 to determine just what they are when he discovered the active alkaloid in the peyote cactus responsible for its intoxicating effects and named it mescaline. As with many aspects of society there has been a dramatic and often contentious relationship between 'western' society and psychedelics. In the early to mid-20th century, they were seen as valuable medicines with great potential for healing, and as scientific tools for understanding in the nascent field of neuroscience. As the counterculture of the 1960s embraced psychedelics as elements of youthful protest, governments around the world labeled them as dangerous, with no medical value. That ultimately led to severe legal penalties for their possession and essentially halted any significant scientific advances. No clinical studies were carried out for nearly 20 years, with very few preclinical studies performed by only a handful of researchers. As the political climate changed, clinical trials were once again allowed, culminating in several high profile published studies on the efficacy of psychedelics to treat psychiatric disorders. Around that time a paradigm shift in the acceptance of psychedelics as medicines to benefit society began to occur, spurring the rapid growth of the ecosystem surrounding psychedelics research. This review presents an overview of the last 125 years of psychedelic science, with key events and findings along the way highlighted leading to a greater understanding of their pharmacology, chemistry, and therapeutic potential.