Surprising new studies show that privileged adolescents are more likely than any other socioeconomic group to suffer from depression, anxiety disorders, and substance abuse. This article presents an interview with Madeline Levine, a Marin County, California, clinical psychologist of 25 years, and author of the new book "The Price of Privilege" (HarperCollins), about what it means to teach kids and teens in some of the priciest school districts and private schools in the country.