Young athletes' mental well-being is associated with smartphone social networking application usage and moderated by performance level and app type.

Smartphones and social media have become an integral part of human daily life and they influence mental well-being. These accounts have been researched in the general population, but not in athletes. This is critical given enhanced physical and emotional stressors in athletes versus non-athletes. Therefore, we here studied intra- and interindividual relationships of four social media sites (WhatsApp, TikTok, Instagram, and Snapchat) with mood, stress, recovery, and sleep using log-based media usage tracking as an objective measure in 53 competitive athletes aged 12-27 years. Multilevel modeling revealed that intraindividual TikTok usage negatively predicted sleep (β = -0.10, p = 0.040) and recovery (β = -0.15, p < 0.002), and positively predicted stress (β = 0.12, p = 0.018). Interindividual Instagram usage predicted feelings of calmness (β = 0.27, p = 0.029) and valence (β = 0.20, p = 0.043). Intriguingly, competition level moderated the usage outcomes of all four apps: Athletes on low performance levels showed lower mental well-being when using social media longer, yet in national and international athletes the strength of these relationships was weaker or even reversed. Our study unravels social media usage associations with mental well-being to vary as a function of performance level and provides findings on intra- and interindividual effects of critical importance to inform future population-tailored and expedient interventions.