Modern science already offers ways to enhance your mood, sex drive, athletic performance, concentration levels and overall health. But is such medically driven self-improvement always a good idea?

For some, it's the last real taste of innocence, and the first real taste of life.

We all imagine better versions of ourselves. Smarter. More attractive. Physically nimble to rock the dance floor, conquer martial arts, or run that ultramarathon. And as we grow older, we want to live ...