Mindfulness buffers the effect of negative affect on rumination: A daily diary study during a mindfulness‐based intervention

Abstract Negative affect automatically triggering rumination is a core pathological mechanism underlying emotional distress. While mindfulness is hypothesized to buffer this process, few studies have dynamically tracked these effects during systematic interventions. The study employed a single‐arm daily diary design during an 8‐week mindfulness‐based intervention (MBI) to investigate whether daily mindfulness buffers the effect of negative affect on rumination. A sample of 116 participants with emotional distress completed daily assessments of mindfulness, negative affect, and state rumination during the MBI. Data were analyzed using linear mixed models (LMMs) and dynamic structural equation modeling (DSEM). LMM results showed that following the MBI, participants' daily mindfulness significantly increased, while daily negative affect and state rumination significantly decreased. Given the single‐arm pre–post design without a control group, these pre–post changes should be interpreted cautiously and cannot be attributed solely to the intervention. DSEM results indicated that higher daily mindfulness buffered the effect of daily negative affect on state rumination. Additional analyses further suggested that different mindfulness components played distinct roles in the onset and maintenance of rumination. These findings highlight the protective role of mindfulness in weakening maladaptive rumination, thereby promoting overall psychological well‐being.