Researchers from the University of Georgia in the US, analysed data from a survey of over a million US teens.
The survey asked students questions about how often they spent time on their phones, tablets and computers, as well as questions about their in-the-flesh social interactions and their overall happiness.
On average, they found that teens who spent more time in front of screen devices - playing computer games, using social media, texting and video chatting - were less happy than those who invested more time in non-screen activities like sports, reading newspapers and magazines, and face-to-face social interaction.
"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," said Jean M Twenge, professor at San Diego State University in the US.
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Total screen abstinence does not lead to happiness either, Twenge found. The happiest teens used digital media a little less than an hour per day.
However after a daily hour of screen time, unhappiness rises steadily along with increasing screen time, according to the study published in the journal Emotion.
"Aim to spend no more than two hours a day on digital media, and try to increase the amount of time you spend seeing friends face-to-face and exercising - two activities reliably linked to greater happiness," he said.
Looking at historical trends from the same age groups since the 1990s, researchers found that the proliferation of screen devices over time coincided with a general drop-off in reported happiness in US teens.
Specifically, young people's life satisfaction, self- esteem and happiness plummeted after 2012.
That is the year that the percentage of Americans who owned a smartphone rose above 50 per cent, Twenge said.
"The advent of the smartphone is the most plausible explanation for the sudden decrease in teens' psychological well-being," she added.