A daily diary study of reciprocal associations between young adults’ loneliness and problematic social media use through psychological distress symptoms: The buffering roles of mindfulness and self-compassion.

= 20.95 years old, 51.2% female), with psychological distress symptoms (PD) tested as a mediator and mindfulness and self-compassion explored as buffers. Results of dynamic structural equation modeling analyses indicated reciprocal positive associations between loneliness and PSMU across days at within-person level. PD mediated such associations, with a stronger indirect effect from PSMU to loneliness (vs. reverse) through PD. At between-person level, mindfulness and self-compassion attenuated the cross-day indirect effect from PSMU to loneliness (rather than reverse) via PD by buffering the same-day positive association of PSMU with PD. Between-person mindfulness and self-compassion also alleviated the same-day positive association between loneliness and PD, but no significant conditional indirect effects emerged for the cross-day pathway from loneliness to PSMU through PD. At within-person level, although self-compassion (rather than mindfulness) buffered the same-day positive association of PSMU (or loneliness) with PD, no conditional cross-day indirect effects emerged. These findings provide insights into how and why young adults' daily loneliness and PSMU perpetuate each other. Improving young adults' mindfulness and self-compassion skills and reducing their PD could help diminish vicious cycles of daily loneliness and PSMU. (PsycInfo Database Record (c) 2026 APA, all rights reserved).