In her Twitter feed, psychologist Jean Twenge summarized the content of her article on the rise in teen depression. The National Survey on Drug and Health Use screens adolescents (ages 12 to 17) using clinical criteria for major depressive episodes 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 from 2009-2019, the US economy was steadily improving.

Is rising depression 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 from 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. 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.