Beyond Depression: What do those mood drugs really do?

A brand-new drug can be like a license to print money. It certainly worked that way for Eli Lilly. When the company launched the antidepressant Prozac in 1987, nobody else had anything quite like it, and Lilly cleaned up. But then other pharmaceutical firms rushed in with their own versions, including Zoloft, Paxil, Celexa and the recently newsworthy Luvox, found in the blood of Columbine High School shooter Eric Harris. The competition has already eaten into Lilly's market share, and things can only go downhill from here.

That's true, if you're talking about Prozac simply as an antidepressant. But if a...