The Karolinska Institutet in Sweden is considered one of the world’s foremost medical research institutes. Within the Institutet, Dr. Torkel Klingberg, a professor of cognitive neuroscience, is considered a leading expert on brain plasticity in childhood development.

Earlier this month, Dr. Klingberg and his colleagues at the Karolinska Institutet dropped a bombshell study into the middle of a massive global debate about the impact of smartphone addiction on children.

Appearing in the journal, Pediatrics, the report is a longitudinal study spanning four years, with an average starting age of 9.9 years. More than 8,300 children in the U.S. participated, completing a self-reported Youth Screen Time Survey, which showed an average of:

• 2.3 hours per day watching videos or television
• 1.5 hours per day playing video games
• 1.4 hours per day engaging in social media

That totals 5.2 hours per day on smartphones or other devices, including tablets, computers, and gaming consoles.

ADHD symptoms were assessed with a parent-completed Child Behavior Checklist at four consecutive annual appointments. The results have the potential to change the narrative in the current debate over children’s use of smartphones. The results showed:

• No impact on ADHD from watching videos or television
• No impact on ADHD from playing video games
• Significant and cumulative impact on ADHD from social media use

“Average social media use was associated with increased inattention symptoms over time, with a cumulative four-year effect,” the researchers write. Let’s take another look at that sentence, piece by piece.

“Average social media use” means not high use, not exceptional use, but average use leads to “increased inattention problems.” And those problems multiply steadily with time — for average users.

Almost as shocking as the results for social media are the results for gaming or watching videos. While these activities can be all-consuming for some children, for the average child they are not associated with any increase in ADHD.

Reaction to this study has been, shall we say, intense. For their story on the study, Futurism chose the headline, “Social Media Is Absolutely Nuking Children’s Brains, New Research Finds.” They added the warning:

[E]xposing young brains to social media could have major mental health implications.

In a blog post, Dr. Klingberg noted, “[I]t is specifically social media that affects children’s ability to concentrate.” He speculated that the “constant distractions” from platforms such as Instagram, Snapchat, TikTok, Facebook, X (Twitter), or Messenger affect the ability to stay focused.

The research comes as social media companies are battling in court with parents, school districts, and state governments over damages supposedly caused by children’s social media use. While the study will be a welcome relief for game makers, it will certainly add momentum to the efforts to ban social media for children.

Written by Steve O’Keefe. First published December 16, 2025.

Sources:

“Digital Media, Genetics and Risk for ADHD Symptoms in Children — A Longitudinal Study,” Pediatrics, December 8, 2025.

“Using social media may impair children’s attention,” News from Karolinska Institutet, December 8, 2025.

“Social Media Is Absolutely Nuking Children’s Brains, New Research Finds,” Futurism, December 9, 2025.

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