Percentage of major depressive episode in the past year among U.S. girls aged 12 to 17, 2008 to 2010 Between 2008 and 2010, an annual average of 12% of U.S. girls aged 12 to 17 experienced at least one episode of major depression, nearly three times the rate for boys in that age group. The percentage of girls who experienced major depression tripled between the ages of 12 and 15 (from 5.1% to 15.2%), with the rate highest at age 16. (Adapted from Center for Behavioral Statistics and Quality, 2012)