In September of 1989, Joe Wesbecker, a long-time employee at the Standard Gravure printing plant in Louisville, Kentucky, walked into work carrying an AK-47 and three spare clips. He opened fire on his coworkers, killing eight, maiming two, and wounding ten more. The assault ended when Wesbecker shot himself with an automatic pistol.

The incident mimicked other workplace shootings except for one key factor: Wesbecker, who had been diagnosed with depression, had just recently started taking the antidepressant drug Prozac. Claiming that the drug was responsible for Wesbecker’s violent behavior, the widows of Wesbecker’s victims brought suit against Eli Lilly, the company that makes Prozac. Eli Lilly won the suit after a settlement had been made in which the company paid the plaintiffs to exclude certain evidence from the trial.

The Wesbecker suit marked the first of several allegations that Prozac incites violent behavior&mdash...