PW: You've said that you wrote The Noonday Demon because it was the book that you wanted to read, but couldn't find, when you became depressed. Its scope is unusually broad, moving from autobiography to sociology to literary criticism. Did you envision this wide range of approaches when you began writing it?

AS: I started off with a fairly broad agenda but it quickly grew. I began by writing about my own experience, then interviewed other people, and then went onto the obvious biochemical issues and the psychology. From there I began to see that the book could really be a window on the human experience. Most books on depression focus on one idea—causes, self-help, science—but I wanted to grapple with the complexity of the illness and the question, what does it mean to be human?

PW: How much basic research did you have to do to gain an understanding of the science and chemistry of depression?

AS: It's funny, I went to a serious scientific conference five years ago and the very topics of the papers seemed hilarious in their obscurity. But toward the end of writing the book, I went back to interview many of those same people and their material seemed straightforward. I essentially changed my whole educational focus and became conversant with scientific knowledge I would never have dreamed of knowing before. This is one of the ways that the book grew and made me understand the complexity of the issues as well as my own involvement with them.

PW: Up until now, you've been known as a novelist and as a social commentator. Do you think that The Noonday Demon will change how people see you as a writer?

AS: I hope so. I'll go on writing fiction, but my dream for my writing is—and I hope this doesn't sound grandiose—that it will change people's lives. I stumbled on this topic because of personal experience, but I would like to see myself as someone whose writing serves a moral purpose in the world.

PW: What surprised you most in your research?

AS: I think I was most surprised by the pervasiveness of the illness across all cultures and boundaries and by the complex evolutionary questions about the functions of moods. I was also surprised in discovering how many different treatments were effective. I came out thinking that there are a million different remedies and some work for some people and some for others. I did not imagine that possibility before.

PW: Is writing ever a way to overcome depression?

AS: Communicating is one of the best ways to overcome depression—talk therapy, companionship, being able to express what you are experiencing. There is no question that being able to get things down on paper gives you control you didn't have before. Certainly that was most satisfying to me as a writer and why I got into this business.