Antidepressant

An antidepressant is a medication designed to treat or alleviate the symptoms of clinical depression. Many antidepressants also are used for the treatment of anxiety disorders.

History 

Like many psychiatric drugs, antidepressants were discovered by accident. The first useful antidepressant group, Monoamine Oxidase Inhibitors (MAOI) were discovered in the early 1950's, and were originally developed to treat tuberculosis. The next group were the Tricyclic antidepressants. They were effective and safer than the MAOIs but still quite dangerous in overdose. They are still used today but have been largely replaced by Selective Serotonin Reuptake Inhibitors (SSRI). The first SSRI was fluoxetine (Prozac).
The three main classes of antidepressants have similar abilities to improve depressed mood, but the newer types are generally considered to have less severe side-effects and be less risky if taken in overdose.