The Centers for Disease Control and Prevention released a report in February that showed an increase in teenagers struggling with their mental health, and the American Academy of Pediatrics has declared mental health challenges for teens a "national emergency." Peter Gray, research professor at Boston College, co-founder of the group Let Grow and the author of books including Free to Learn (Basic Books, 2015), argues one major reason kids are facing these issues is the decline in freedom that kids and teens now have to do things on their own or with friends.