Bidirectional associations between smartphone usage and momentary well-being in young adults: Tackling methodological challenges by combining experience sampling methods with passive smartphone data.

Given the pervasive role of smartphones in modern life, research into their impact on well-being has flourished. This study addresses existing methodological shortcomings using smartphone log data and experience sampling methods (ESM) to explore the bidirectional within-person relationship between smartphone usage and momentary well-being variables (i.e., affect valence, loneliness, positive affect, and negative affect). We further examine different categories of smartphone usage, namely, communication, social media, and other apps. We analyze three samples (N₁ = 225, N₂ = 17, N₃ = 13; with T₁ = 7,874, T₂ = 2,566, T₃ = 1,533 ESM reports) with multilevel models to test our preregistered hypotheses. Data for Sample I were collected in Spain in 2022 (82% female; M_age = 23.1). Samples II and III (80% female; M_age = 21.6) were collected in the Netherlands between 2021 and 2022. Our results suggest that smartphone usage within an hour before ESM assessment, especially using social media apps, is associated with reduced affect valence and increased loneliness on a within-person level. Loneliness was associated with more smartphone usage than usual, particularly the use of social media apps, within the hour following ESM assessments. However, overall, our findings indicate weak bidirectional associations between smartphone usage and indicators of momentary well-being (range standardized β = .00-.08). On the between-person level, those individuals generally high in loneliness were more affected in their momentary loneliness by prior social media use, suggesting a heightened social media sensitivity. The interplay between social media use and momentary loneliness should be studied in more detail, including contextual factors and experimental designs. (PsycInfo Database Record (c) 2025 APA, all rights reserved).