By Charles Barber - For the last three decades, Victoria Arango has been studying the brains of people who committed suicide, and has discovered that the biochemistry of their brains differs significantly from that of people who don't commit suicide.

I'm at the New York State Psychiatric Institute in northern Manhattan. My guide, Victoria, has been studying the brains of people who committed suicide, and has discovered that the biochemistry of their brains differs significantly from that of people who don't commit suicide. But there are aspects of their work that trouble me. Could our brains be so sick that they'll kill us? How much do our brain chemicals control our lives, and what control is left to us?

A project studying the brains of people who committed suicide raises basic questions about how much brain chemicals control our lives and what control is left is to us.