Screen use, lifestyle habits and mental health in preschool children: a cross-sectional study

Background Excessive screen exposure is associated with sleep disturbances, unhealthy dietary patterns, reduced physical activity, and poorer socio-emotional wellbeing. This study aimed to: (1) assess the association between screen time and lifestyle habits, and (2) examine the associations of screen time and lifestyle habits with emotional and behavioral difficulties in preschool children. Methods This cross-sectional study included 931 children (2–6 years) from Portugal. Parents completed questionnaires on children’s lifestyle habits and emotional and behavioral difficulties using the Strengths and Difficulties Questionnaire (SDQ). Anthropometric measurements were collected. Screen time was classified as low (≤ 60 min/day), moderate (> 60 to < 120 min/day), or high (≥ 120 min/day). Linear and logistic regression models adjusted for age, sex, body mass index, and parental education were performed. Results Regarding lifestyle habits, high screen time was associated with shorter weekday sleep duration and higher consumption of ultra-processed foods. No significant associations were observed with active play time or participation in extracurricular sports after adjustment. Regarding mental health, children with high screen time had higher odds of abnormal SDQ scores, indicating greater emotional and behavioral difficulties. Longer weekend sleep duration and lower maternal educational level were independently associated with SDQ categories. Conclusions Higher screen time was associated with shorter weekday sleep duration, higher consumption of ultra-processed foods, and greater emotional and behavioral difficulties in preschool children. These findings support current recommendations promoting balanced screen use and healthy lifestyle habits during early childhood while highlighting the importance of family and sociodemographic factors for children’s mental health.