twenge, a year ago published -- i will put this up on the screen. you published an analysis of 13 other possible explanations, and then with data you ruled them all out, although there's one that's tantalizing. that's alternative number six. i am putting that up on the screen right now. that's the, it is because children and teens have less independence. of the 13 that get bandied about, this one you thought might have some merit. i guess you actually read these together, a different parenting style and the age of technology. explain. >> yes. first, i want to point out that one reason a lot of the other 12 explanations fail is that they're focused just on u.s. things like, you know, the political climate or school shootings, but it turns out the increase in depression and loneliness among teens is worldwide. it shows up in international data, country after country. very little happened until 2012, and then depression and anxiety and loneliness. so that explanation around independence, it is true that teens now, compared to previous generations, are