New research finds teens who spend more time online are less happy. Sleep deprivation may be part of the problem.

Worried that your teenager seems unhappy, and/or sleep deprived, much of the time? If your first impulse is to go online to look for help, you might want to take a step back.

The answer you seek may not be on the Internet. It may actually be the Internet.

Two large-scale studies released this week offer compelling, if not definitive, evidence that too much time spent online is harmful to adolescents' physical and/or emotional health. Canadian researchers report the more time teens spend online, the more likely they are to get too little sleep.

And an American research team finds psychological well-being of American adolescents "suddenly declined in 2012" and continued a downward trend through 2016. During that same period, smartphone ownership increased rapidly, from 50 percent of the United States' population to 77 percent.

The scholars, led by psychologist Jean Twenge of San Diego State University, strongly suspects those two trends are related. "The rapid adoption of smart-phone technology in the early 2010s may have had a marked negative impact," they write in the journal Emotion.

Twenge and her colleagues analyzed data from the Monitoring the Future project, an annual, nationally representative survey of 1.1 million eighth, 10th, and 12th grade students. The kids answered a series of questions revealing their levels of self-esteem, happiness, and satisfaction with various elements of their lives.

"After staying steady or rising between 1991 and 2011, adolescents' psychological well-being dropped noticeably between 2012 and 2016," they report. "Self-esteem declined after 2012, as did measures of self-satisfaction, life satisfaction, and domain satisfaction." The latter category included large declines in "satisfaction with life as a whole, friends, amount of fun, self, and personal safety."

In a second study, the researchers looked at the respondents' media usage, including how much time they watched television, and the amount of time they spent on the Internet "not counting work for school or a job." The kids also reported how much time they spend on homework, and how often they engage in offline activities such as playing sports and socializing with friends.

"Adolescents who spent more time on electronic communication and screens (social media, texting, electronic games, the Internet) were less happy, less satisfied with their lives, and had lower self-esteem, especially among eighth and 10th graders," Twenge and her colleagues write. "In contrast, adolescents who spent more time on non-screen activities such as in-person social interaction, sports/exercise, print media, and homework had higher psychological well-being. Among eighth and 10th graders, every non-screen activity as correlated with greater happiness, and every screen activity was correlated with less happiness."

Correlation does not prove causation, of course; it's possible that unhappy teens, who feel they don't fit in with friends or family, choose to spend more time online. But the researchers note that previous evidence "suggests the causal arrow points from electronic communication to lower psychological well-being, rather than the other way around."

But that still leaves the question of why. Another new study, in the journal Acta Pediatrica, suggests part of the answer may be that Internet-addicted teens aren't getting sufficient sleep.

A research team led by Hugues Sampasa-Kanyinga of the University of Ottawa examined data from the 2015 Ontario Student Drug Use and Health Survey, which featured answers from 5,242 students aged 11 to 20 from around the province.

They report nearly two-thirds of respondents—63.6 percent—failed to get the recommended amount of sleep for their age group. Strikingly, the more time they spent on social media, the less time they spent sleeping.

The researchers list several possible explanations. Using social media late at night could shift kids' circadian rhythms, delaying the onset of sleep. "The blue light of screen devices has been shown to suppress the release of melatonin," they note.

Once again, these findings do not prove causality. But they certainly raise concerns.

Twenge's study found the most well-adjusted kids are those who used the Internet a bit less than an hour per day. That's very likely because they aren't missing out on the aspects of life that are linked with happiness and satisfaction, including exercise, socializing—and snoozing.