Objective risk and protective factors for momentary and daily loneliness:using digital phenotyping and temporal analysis.

Loneliness is a growing global health issue, yet real-time assessments of its objective risk and protective factors are limited. This study identifies momentary and daily predictors using digital phenotyping and temporal analysis. Analyzing 12788 momentary observations from social mobile sensing and actigraphy, we examined how they impact loneliness on average (between-person) and in daily fluctuations (within-person). Instant messenger app usage was associated with increased loneliness, both momentarily (B = 2.95, p = 0.017) and daily (B = 2.83, p = 0.018), within and between subjects. Social media usage was associated with higher within-person momentary loneliness (B = 0.53, p = 0.001). An exploratory network analysis suggested that physical activity is associated with in-person social interaction, which is negatively associated with loneliness, while social media may replace social interactions. Thus, objective risk factors include increased use of social media and instant messaging, whereas greater physical activity may serve as a protective factor.