Many measures of adolescent mental health began to deteriorate sometime around 2009. It is true of the number of U.S. high-school students who say they feel persistently sad or hopeless. It’s also true of reported loneliness. And it is true of emergency room visits for self-harm among Americans ages 10 to 19. This timing is suspicious because internet use among adolescents was also starting to soar during the same period. Apple began selling the iPhone in 2007. Facebook opened itself for general use in late 2006, and one-third of Americans were using it by 2009. Continue reading →