S1 Dataset -

Objectives
Rumination is suggested to exacerbate psychological health, but there is room for investigating the potential protecting factors for individuals with high ruminative tendencies against psychological symptoms. The present cross-sectional study aimed to uncover the associations between rumination as a maladaptive dimension of self-focus, self-compassion, and psychological health, and whether and how components of self-compassion may moderate the associations between rumination and psychological health in Japanese undergraduate students.
Methods
A questionnaire survey was conducted by using both an online platform and a paper-based questionnaire. The survey included established Japanese versions of psychological scales on rumination, self-compassion, perceived stress, trait anxiety, and depression.
Results
The results revealed statistically significant positive correlations between rumination and negative dimensions of self-compassion, and rumination and psychological symptoms. Positive dimensions of self-compassion were significantly negatively correlated with both rumination and psychological symptoms. Reflection as a positive dimension of self-focus did not show significant correlations with most psychological variables. Furthermore, hierarchical multiple regression analyses involving subscales of self-compassion and their interactions with rumination as predictors revealed that the interactions between rumination and components of self-compassion, i.e., over-identification and mindfulness, significantly predicted trait anxiety. Higher rumination predicted higher anxiety when over-identification was high, but not when over-identification was low. Also, lower rumination predicted lower anxiety when mindfulness was high, but not when mindfulness was low.
Conclusions
The results suggest significant associations between rumination, components of self-compassion, and psychological health in a population of Japanese undergraduate students. The data also suggest that components of self-compassion play moderating roles in the relationship between rumination and psychological health, potentially serving as aggravating/protective factors for psychological health. Longitudinal studies and comparisons between different cultures should be conducted in the future quest.