Of course, correlation doesn’t prove causation – perhaps unhappy people use digital media more. However, several experiments and longitudinal studies have concluded that digital media use leads to unhappiness, but unhappiness doesn’t lead to digital media use. As I document in my book, iGen (about the post-millennial generation born after 1995), there are also troubling trends in teenagers’ mental health. Between 2011 and 2015, rates of serious depression, self-injury (such as deliberately cutting oneself), and suicide all skyrocketed among American teenagers.