Student Kahlil Quato fights tears as he speaks at a University of Chicago candlelight vigil in 2007. The service was held in remembrance of Amadou Cisse, a graduate student, who was shot to death at point-blank range. Stacie Freudenberg/AP hide caption

itoggle caption Stacie Freudenberg/AP

Talk therapy is best for some people; antidepressants are better for others. Scientists say PET scans might help figure out early on what treatment a person needs. iStockphoto.com hide caption

itoggle caption iStockphoto.com