To no parent's surprise, too much smartphone use makes teens unhappy.
Teens with screens
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So says a new study from San Diego State University, which pulled data from over one million 8th-, 10th-, and 12th-graders in the U.S. showing teens who spent more time on social media, gaming, texting and video-chatting on their phones were not as happy as those who played sports, went outside and interacted with real human beings.

But is it the screen time bringing them down or are sadder teens more likely to insulate themselves in a virtual world? Lead author of the study and professor of psychology Jean M. Twenge believes it's the phone that contributes to making them unhappy, not the other way around.

"Although this study can't show causation, several other studies have shown that more social media use leads to unhappiness, but unhappiness does not lead to more social media use," Twenge said.

Though abstinence doesn't seem to fix the problem, either, as noted in the study, there's something to Twenge's theory. Another recent study by the U.S. Centers for Disease Control and Prevention and also lead by Twenge, found a spike in depression and suicide among teen girls increased the more time they spent on their phones.

That's alarming, especially considering the age in which kids get smartphones has continued to climb lower - dropping from 12 in 2012 to 10.3 years in 2016.

Twenge has been studying teen behavior since the early 90's and has been on the forefront of research suggesting an abrupt change in behavior and emotional states of teenagers due to smartphone use. She says there's been a dramatic shift starting in 2012 when younger and younger kids starting getting more screen time.

Researchers found more of the same while sifting through the data for this study. Teenagers' life satisfaction, self-esteem and happiness plummeted after 2012.

To back up that work, Twenge's previous studies suggest kids who spend at least four or five hours on their phone increase their risk factor for suicide by a whopping 71 percent, regardless of whether it was cat videos or something else. It was the time spent on the device, not the content, that mattered most.

"By far the largest change in teens' lives between 2012 and 2016 was the increase in the amount of time they spent on digital media, and the subsequent decline in in-person social activities and sleep," Twenge said. "The key to digital media use and happiness is limited use."

She suggests teens aim to spend no more than two hours a day on digital media, exercise more and try to hang out with friends face-to-face to increase happiness - all things adults could probably use more of as well.