Cocaine

Sigmund Freud, the founder of psychoanalysis, was one of the first scientists to experiment with cocaine, which comes from the leaves of the Erythroxylon coca plant. He was impressed with the stimulant properties of the drug, and because these properties were opposite to the depressant properties of alcohol and opiates, he reportedly proposed that cocaine be used as an antidote or cure for alcoholism or opiate addiction. He even suggested this to some friends who took his advice. Unfortunately, Freud realized his mistake when cocaine proved to be addicting. This highlights the fact that different addicting drugs can have different acute effects—even opposite ones—and yet, they share the same addicting property. Fortunately, today we have behavioral tests in animals that detect possible addicting substances before they are given to people.