82.5: The percentage of children and young adults who exhibit significant symptoms of mental illness at some point between the ages of 9 and 21. The startling statistic comes from a collaborative study conducted by Duke University and the North Carolina Department of Health and Human Services, which surveyed 1,420 children over 12 years beginning in 1993. Investigators checked in up to nine times to test for anxiety, depression, addiction, obsessive-compulsive disorder, and more. The results: 61.1 percent met the diagnostic criteria for mental illness during at least one appointment, while an additional 21.4 percent had problems bad enough to interfere with school, social life, or family relations. Just like physical disease, mental illness affects nearly all of us at times, says study coauthor and psychologist E. Jane Costello. “We have to destigmatize the idea of mental disorder,” she says. “We shouldn’t be surprised that the brain has problems, just like the rest of the body.”