Screen time, smartphone addiction, and executive-motor function in Tunisian middle school students

This study advances beyond general screen time metrics by investigating the specific associations between smartphone addiction and objectively measuring daily screen time and core neurocognitive and graphomotor functions in adolescents. In a cross-sectional study involving 270 Tunisian middle school students (mean age = 14.8 ± 0.5 years; 54% male and 46% female students) recruited from three public middle schools in the region of Sfax, Tunisia, during routine school health assessments (December 2023-March 2024), participants were classified as smartphone-addicted (n = 120) or non-addicted (n = 150) using a standardized scale, and their actual screen time was recorded from their devices. All participants completed assessments measuring sustained attention, selective attention, handwriting quality and speed, and abstract reasoning. The results showed that the addicted group demonstrated significantly poorer sustained attention (correct items: 177 ± 16 vs. 195 ± 19.4, p < 0.001), more errors in selective attention (interference errors: 3.0 ± 2.0 vs. 2.38 ± 1.80, p < 0.001), and reduced handwriting quality (errors: 13.0 ± 8.0 vs. 10.24 ± 7.09, p = 0.016). On the other hand, no differences emerged in abstract reasoning or handwriting speed. Regression analyses confirmed that both higher addiction severity and longer screen time were significant negative predictors, in separate models, of sustained attention (R ² = 0.27-0.34, p < 0.001), selective attention (R ² = 0.15-0.16, p < 0.001), and handwriting quality (R ² = 0.06-0.07, p < 0.001), but not of abstract reasoning. These findings demonstrate that smartphone addiction and excessive screen time are both associated with significant deficits in key attentional and motor skills, underscoring the critical need for targeted interventions focusing on healthy digital habits to safeguard cognitive-motor development in educational settings. The cross-sectional design precludes causal inference, and the high correlation between addiction severity and screen time indicates they are intertwined aspects of digital engagement.