Thread by @jean_twenge

Just out: Depression among U.S. teen girls doubled from 2009 to 2019 and was up 74% among teen boys, according to just-released data from the gov't administered National Survey of Drug Use and Health. What does this mean?

NSDUH screens adolescents (ages 12 to 17) using clinical criteria for major depressive episode in the last year. Twice as many teen girls in 2019 (vs. 2009) have clinical-level depression, and 74% more teen boys do as well. Why?

The 2019 data makes it clear that the rise in teen depression is not due to the Great Recession. In fact, it's exactly the *opposite* of what you'd expect if teen depression were caused by economic struggles: As depression rose 2009-2019, the U.S. economy was steadily improving.

Is rising dep. due to academic pressures? One measure of academic pressure is homework time, which has not changed consistently over this time period -- it's actually down among 8th graders 2009-2018, and has ups and downs among 10th & 12th graders.

So what did change in teens' lives over this time period when depression increased so much? In 2009, only about half used social media every day; now about 85% do. In 2009, most did not own a smartphone; now about 95% do. #iGen #GenZ

It's not just that the two trends happened at the same time -- it's that the rise of smartphones and social media had an enormous impact on day to day life for teens. More in my book, iGen, and in this article: sciencedirect.com/science/articl…

Because we can't randomly assign people to be born at different times, we can't prove causation. We have to go on the data we have -- and the rise of smartphones & social media had the biggest impact on the most teens, and is thus the most likely to impact mental health.

Are there other possible causes? Sure. But it's tough to think of anything else that changed consistently over this time period that had as big an impact on so many people. No matter what the cause: We need more resources for teen mental health. This can't continue.