Time spent, not use frequency: Associations between social media use and anxiety and depressive symptoms across age groups in the Czech population.

Social media use may facilitate connection and access to information while also being associated with poorer mental health. This study examined associations between social media use and anxiety and depressive symptoms across age groups in the Czech population aged 16 years and older. Cross-sectional data were collected through a computer-assisted web survey conducted in January 2025 among 2867 respondents aged 16 years and older. Anxiety and depressive symptoms were assessed using the GAD-7 and PHQ-9 scales. Internal consistency was high (GAD-7: α = 0.914, ω = 0.916; PHQ-9: α = 0.877, ω = 0.883), and confirmatory factor analysis supported correlated but distinct anxiety and depressive-symptom factors. The original quasi-Poisson and Kruskal-Wallis analyses were retained, while the extended analysis added structural equation modelling (SEM), HC3-robust regression, formal age-interaction tests, and survey-weighted sensitivity analyses. In the primary SEM (n = 1758), longer daily social media use was independently associated with higher latent anxiety (β = 0.155, p < .001) and depressive symptoms (β = 0.138, p < .001), whereas use frequency was not independently associated with either outcome. Profile visibility and perceived societal influence of social media showed no consistent adjusted associations. Age-stratified estimates suggested weaker time-anxiety associations among respondents aged 65 years and older, but formal interaction tests did not confirm significant age moderation. The findings indicate that duration of exposure may be more consistently associated with anxiety and depressive symptoms than use frequency. Because the design is cross-sectional, causal direction cannot be established, and reverse or reciprocal relationships between social media use and mental-health symptoms remain possible.