Mindfulness and Psychosocial Symptoms in People with Cancer: Testing Rumination and Experiential Avoidance as Mediators, and Sex as a Moderator.

While Mindfulness-Based Interventions (MBIs) are evidenced to reduce common psychosocial symptoms experienced by people with cancer (PWC), few studies have tested their mechanisms. Additionally, studies have yet to assess sex assigned at birth as a moderator of the relationship between mindfulness and psychosocial symptoms through specified mediators. This study (1) explored the mediating role of rumination and experiential avoidance (EA) in the relationship between mindfulness and a range of psychosocial symptoms and (2) tested sex as a moderator of the mediation models. This cross-sectional study assessed baseline data from 134 participants recruited for a mindfulness app clinical trial. Validated patient reported outcome measures of trait mindfulness, rumination, experiential avoidance, depression, anxiety, FCR, and fatigue were collected. Structural Equation Modelling was employed in R. Rumination was a significant partial mediator between mindfulness, depression and anxiety and FCR, but not fatigue. EA acted as a weak mediator from mindfulness to FCR only. Subgroup analyses found that rumination may be more important for females than males in the relationship between mindfulness and depression and anxiety. Rumination may be a stronger mediator than EA for anxiety, depression and FCR, and this may be particularly important for females. Findings may help MBI researchers and developers target potentially relevant mediators to maximize robust study design and intervention efficacy.