In 2010, something changed. It was not sudden, nor was it instantly clear. But over the years, that change became impossible to miss.
The incidence of anxiety among teenagers started to increase. Depression followed. By 2015, adolescent mental health had plummeted, and those watching the data were feeling confounded. What had happened?
Some cited academic pressure. Others pointed to helicopter parenting or economic anxiety. But the answer, as it turned out, had been sitting quietly in the hands of almost every teenager in the developed world.