Africa Studio/Shutterstock
Source: Africa Studio/Shutterstock

Not many research results make you sit up straight in your chair, but this one did.

I’ve been tracking trends in the attitudes and behaviors of teens and young adults for many years, primarily relying on a nationally representative survey of U.S. teens conducted every year called Monitoring the Future (MtF) that has surveyed 1.4 million teens since the 1970s. Around 2012 to 2013, there was sudden uptick in teens saying they were experiencing symptoms of depression — feeling hopeless, not enjoying life, believing they can’t do anything right. Depressive symptoms continued to increase over the next few years, making today's teens — whom I describe in my new book, iGen — significantly more depressed than teens just a few years before.

Since an excerpt of iGen ran in the Atlantic, some have wondered how I came to the conclusion that mental health issues were on the rise among teens (and why). Now that the book has been published with all of the graphs and analyses, I can finally explain that here, which I hope will answer critiques that seemed to be based on an incomplete understanding of the research and how it was done.

As I found when I dug deeper, the increase in depressive symptoms was only part of the story. Happiness — which had been increasing among teens for 20 years — began to decline. Loneliness spiked sharply, and more entering college students (in the national American Freshman survey of 9 million students) said they felt depressed and overwhelmed. Even more concerning, 50 percent more teens in 2015 (versus 2011) demonstrated clinically diagnosable depression in the NS-DUH national screening study. (It's important to note that all of these sources are surveys of unselected samples of teens and not those who seek treatment — thus they cannot be explained by greater treatment-seeking). The teen suicide rate tripled among girls ages 12 to 14 and increased by 50 percent among girls ages 15 to 19. The number of children and teens hospitalized for suicidal thoughts or self-harm doubled between 2008 and 2015. iGen'ers were experiencing a mental health crisis. As if that weren’t enough, no one seemed to know why.

Economic causes seemed unlikely; the U.S. economy improved after 2011. It wasn’t academic pressure, either; in the MtF surveys, teens in the 2010s say they do fewer hours of homework than teens reported in the 1990s, and the time college-bound high school students spend on extracurriculars — contrary to popular belief — is about the same in the American Freshman survey. There was no cataclysmic event or political shift during that time (these data predate the presidential election). Factors such as income inequality and shifting family structure, mentioned by some, had been building for decades, with no sudden shift in the 2010s. So what was it?

Then it hit me. In another project, I’d found that teens were spending less time with their friends in person and more time communicating electronically, with these trends accelerating after 2011. That, I realized, was around the time that smartphones became ubiquitous — when many teens (and adults) started spending nearly every waking moment looking at the phones in their hands. Sure enough, the Pew Center found that the percentage of Americans owning a smartphone crossed 50 percent in late 2012. That was also around the time social media became almost mandatory for teens. Smartphones and social media were also something that affected teens directly — a fundamental change in how they spent their time, not just an event in the news or a trend they heard about from their parents.

So the time sequence fit: Right when smartphones became common, and teens started spending less time face-to-face, their psychological well-being plummeted. The next question was whether smartphones might be linked to lower well-being among individuals. In my analyses of MtF and the CDC's Youth Risk Surveillance System data for the book, I found they were — teens who spent more time on screens were less happy, more depressed, and had more risk factors for suicide. Those links remained when possible confounding factors, such as gender, race, and socioeconomic status, were taken into account.

Some wondered why I didn't include studies that found positive effects for social media. First, this was a book excerpt, so not surprisingly I focused on the analyses I did for the book (of the nationally representative MtF and CDC data on thousands of teens, which show correlations between more time on social media and lower well-being). Second, the most recent meta-analysis (of 67 studies) also found a correlation between more time on social media and lower well-being. (For two examples, see this study of adults and this one of tweens). Overall, between the large samples I analyzed and the meta-analysis, it seems clear that the preponderance of the evidence points toward lower well-being with more social media use; thus, the idea that I was selective with evidence is unfounded. Social media may have other benefits, but more psychological well-being — which was my focus — does not appear to be one of them.

Of course, as I also specifically noted in the Atlantic excerpt, correlation doesn’t prove causation. For example, perhaps unhappy people use screen devices more. However, three other studies have effectively ruled out that explanation, at least for social media. Two longitudinal studies found that more social media use led to unhappiness, but unhappiness did not lead to more social media use. A third study was a true experiment (which can determine causation); it randomly assigned adults to give up Facebook for a week, or not. Those who gave up Facebook ended the week happier, less lonely, and less depressed.

Depression causing social media use also can’t explain why depression would increase so suddenly after 2011-12. If the increase in depression occurred first, some other, unknown factor would have to cause depression to rise so sharply, which would then lead to more smartphone and social media use. It seems much more likely that smartphone and social media use went up, and the increase in depression followed. By far the biggest changes in teens’ day-to-day lives between 2011 and 2015 were the spread of the smartphone and the growth of social media. Nothing else even comes close.

Not only that: No one disputes that in-person social interaction is linked to better mental health. So even if we dismiss the correlation between social media and depression — say, calling it neutral — the decline in in-person social interaction could certainly account for the increase in depression and unhappiness. And why has in-person social interaction declined? Probably because screen time increased.

None of this means you should yank the phone out of your teens’ hands. As other studies have also documented, moderate use of smartphones — around an hour a day — is not harmful. In my analyses of data from the Youth Risk Surveillance System survey administered by the CDC, negative effects on mental health appeared only after two or more hours a day of use. Of course, most teens (and many adults) use their smartphones much more than two hours a day (the average is six to eight hours during leisure time), so it makes sense to consider setting limits.

After my book excerpt was published in The Atlantic, some, like Sarah Rose Cavanagh, argued that we shouldn’t draw any conclusions until we can do a controlled experiment randomly assigning groups of teens to extensive or low smartphone use. She concluded, “My suspicion is that the kids are gonna be OK.”

But it is not OK that 50 percent more teens suffered from major depression in 2015 versus just four years before. It is not OK that the suicide rate for teen girls is at its highest level since 1975. It is not OK that twice as many children and teens are now hospitalized for self-harm or suicidal thoughts. It is not OK that more teens say that they are lonely and feel hopeless.

iGen also shows many positive traits and trends, which are detailed in the book, including lower rates of teen pregnancy and alcohol use and a stronger work ethic. Just so there is no misunderstanding: The worrying trends in mental health do not mean there are no positive trends, or that I ignore the positive trends. In fact, Chapter 1 of the book — front and center — highlights many of these positive trends, as does the rest of the book. Nor should documenting the mental health trends be construed as "criticism" of this generation — as a psychologist, I find that idea antithetical to the basis of my field, which is that mental health issues deserve understanding and compassionate help, not censure.

Given the undeniably negative trends in teens' mental health and the evidence suggesting smartphone use is at least partially behind them, it makes sense to limit kids' and teens' smartphone use. As with any intervention, the risks of doing something versus doing nothing must be considered. There doesn't seem to be much risk involved in limiting smartphone use to 90 minutes a day or less. However, doing nothing and having teens continue to spend six-plus hours a day with new media risks having these negative mental health trends continue. 

I would applaud a large, randomized controlled trial that directly addresses the causal link between smartphones and depression. I hope such research will be funded and conducted, though even if it were, it would be years before we knew the results. And if evidence emerges for another cultural or technological trend that can explain the increase in depression, loneliness, and suicide starting around 2012, I will push to address it. Right now, smartphone use is the most likely change agent, so it's the one I'm addressing with my own children, and the one I think other parents should consider. Teens and young adults are telling college counselors, survey administrators, and therapists that they are suffering, and we need to listen.

References

Shakya, H. B., & Christakis, N. A. (2017). Association of Facebook use with compromised well-being: A longitudinal study. American Journal of Epidemiology.

Tromholt, M. (2016). The Facebook experiment: Quitting Facebook leads to higher levels of well-being. Cyberpsychology, Behavior, and Social Networking, 19, 661-666.

Twenge, J. M. (2017). iGen: Why Today’s Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy – and Completely Unprepared for Adulthood. New York: Atria Books.

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