Increases in social-media use and television viewing are linked to symptoms of depression among teens, and researchers believe unrealistic depictions of how others look and behave online and on-screen may be to blame, according to a large-scale Canadian study.

The study, published in the journal JAMA Pediatrics on Monday, analyzed survey data of more than 3,800 Montreal-area teens taken over four years, starting in Grade 7. Using statistical modelling, the researchers found when participants increased their social-media use or their television consumption in a given year, they also had higher levels of depressive symptoms.

The same link, however, was not found for video gaming.

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“It wasn’t all different types of screen time that were related to depression; it was just television and social media,” said senior author Patricia Conrod, a professor of psychiatry at the University of Montreal and Tier 1 Canada Research Chair at CHU Sainte-Justine.

The study provides a deeper look at how the ways in which young people use digital media may affect their mental well-being, instead of merely focusing on the amount of time they spend in front of screens. In a position statement issued last month, the Canadian Paediatric Society noted there are numerous benefits, in addition to risks, of digital-media use, and advised parents to manage not only their children’s screen time, but the content and context of their digital consumption.

Dr. Conrod and her team examined the association between depression and four types of screen activities: social-media use, such as Facebook and Twitter; video gaming; television viewing; and other computer use. Participants were asked how much time a day they spent on these activities. They were also asked to rate the extent to which they experienced various symptoms of depression, such as feeling lonely, sad and hopeless.

Only video gaming was not associated with depression. High average levels of computer use over the four-year period were associated with depression. But any further increase in computer use in a given year was not associated with an increase in depression symptoms.

The researchers also looked at three hypotheses, often used to explain how digital-media use affects young people’s mental well-being. The first was the “displacement hypothesis,” which suggests screen time displaces other activities, such as physical exercise, that have a positive effect on one’s mental health. In their analysis, the researchers found no evidence for this, Dr. Conrod said. If their findings had supported the hypothesis, they would have found high levels of video-game playing to be associated with depression.

The second hypothesis was “upward social comparison,” which suggests being presented with highly idealized portrayals of young people is detrimental to teens’ mental health. The researchers found this may be one likely explanation. For teens, being exposed to a false reality on social media, in which everyone else appears to look better and have more fun than they do, may hurt their self-esteem, Dr. Conrod said.

The third hypothesis they said may be at play was “reinforcing spirals,” which suggests people select and are fed content that aligns with their state of mind. Due to the algorithmic nature of social media, young people who engage in digital activities that promote depression are more likely to be fed further content that promotes depression, Dr. Conrod said.

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Piushkumar Mandhane, an associate professor of pediatrics at the University of Alberta who was not involved in the study, said the latest findings help address a need in the literature for answers about how digital-media content influences children’s mental health.

“It’s probably not sufficient to just say, ‘Let’s meet the guidelines [for limiting screen time],’" Dr. Mandhane said. Rather, he said it is important for parents to also pay attention to the content of their children’s digital-media consumption and to discuss with them what they view online and how it makes them feel.

Michelle Ponti, a pediatrician in London, Ont., and chair of the Canadian Paediatric Society’s Digital Health Task Force, said the new study adds support to the society’s position statement, which suggested interactive video game-playing can offer potential benefits for older children and teens.

“There’s more and more research coming out that video-game [playing] is linked to enhanced well-being, and positive inter-group relations and some increased physical activity and problem-solving,” Dr. Ponti said, adding some researchers suggest it may even improve attention and executive functioning.

However, she emphasized parents and their children should prioritize other activities, including school activities, sleep, sports and socializing. Doing so results in little time left over for screens, she said, noting that when children and teens do use screens, they should think about whether it is for an active, educational purpose.

“The context and the content matter,” she said.

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