How Screen Time Affects the Brain

A review of

Pieh C, Humer E, Hoenigl A, Schwab J, Mayerhofer D, Dale R, Haider K. Smartphone screen time reduction improves mental health: a randomized controlled trial. BMC Med. 2025 Feb 21;23(1):107. doi: 10.1186/s12916-025-03944-z. PMID: 39985031; PMCID: PMC11846175.

By Dr. Bryan Stephens

Summarized Review Conclusions

While research has shown an association of mental health with screen time, a causal relationship had not been further noted. The authors dove deeper to see a causal change rather than just a correlation between the two. Mental health indicators showed an improvement with a reduction in screen time usage of smart phones. The authors noted a small to medium effect on depressive symptoms, stress, sleep quality, and well-being along with it being a causal relationship.

“The study highlights mental health improvements through smartphone screen time reduction. “

“The results suggest a causal relationship, rather than a merely correlative one, between daily smartphone screen time and mental health.”

Introduction to the Research

Multiple studies in the past have associated smartphone screen time with mental health. As smart phone usage and reliance have become a staple to much of the population, an increase in mental health issues have also been noted with it. With the associations noted in the past, a causal relationship between the two had not been thoroughly researched. This article looked at the reduction of screen time and the causal change it has on mental health indicators.

Research Methodology

“This non-blinded, parallel randomized controlled trial (RCT) was performed to investigate the impact of a 3-week screen time reduction to ≤ 2 h/d in healthy students on stress (PSQ), well-being (WHO-5), depressive symptoms (PHQ-9), and sleep quality (ISI) at baseline (t0), post-intervention (t1), and at follow-up (t2 = 6 weeks after t1). For the intention to treat analysis, repeated measures ANOVAs and post-hoc tests (for time as well as group differences) were performed and effect sizes were presented as partial eta squared (η² = time × group) and group-mean differences.”

Research Findings

“In total, 111 out of 125 healthy students (70 females; mean age = 22.68 ± 2.6 years; mean screen time = 276 ± 115.1 min/day) were randomly assigned to intervention—(n = 58; 3 weeks of screen time reduction to ≤ 2 h/day) or control group (n = 53). Although no differences were observed at baseline (t0), significant post-intervention (t1) effects of small to medium size were observed on well-being (η² = .053), depressive symptoms (η² = .109), sleep quality (η² = .048), and stress (η² = .085). Significant group differences (p ≤ .05) were found post-intervention (t1) for depressive symptoms (Mean Difference (MD) = 2.11, Standard Error (SE) = 0.63, 95% Confidence Interval (CI) [0.87, 3.36]), sleep quality (MD = 2.59, SE = 0.97, 95% CI [0.66, 4.51]), well-being (MD = -1.54, SE = 0.68, 95% CI [.-2.89, -0.18]), and stress (MD = 6.91, SE = 3.48, 95% CI [0.01, 13.81]). Screen time increased rapidly after the intervention and at follow-up the values were once again approaching the initial level.”

Research References

As always with these reviews, these are my takeaways from the article and I encourage you to read the article in its entirety. The references used in this article by the authors of this article are listed here.

Our Message

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