The effect of mindfulness and psychological capital on mental health of breast cancer patients: Based on polynomial regression and response surface analysis.

Objective: To explore the combined effects of mindfulness and psychological capital on mental health of breast cancer patients and to examine the mediating effect of positive emotions in their relationship.

Methods: A convenient sampling method was used in this study, and 522 breast cancer patients aged 18 to 59 who received chemotherapy in a tertiary cancer hospital were enrolled. Polynomial regression with response surface analysis was mainly employed to explore the relationship between mindfulness, psychological capital, and mental health. A block-variable approach was used to verify the mediating effect of positive emotions.

Results: In cases of congruence, mental health was better when mindfulness and psychological capital were both high instead of being both low (the slope of the congruence was 0.540, p < 0.001); In cases of incongruence, poorer mental health was found in breast cancer patients with low psychological capital and high mindfulness compared with those who had high psychological capital and low mindfulness (the slope of the incongruence was -0.338, p < 0.001), and the combined effects were a positive curve (positive U-shaped) related to mental health (β = 0.102, p = 0.040). In addition, positive emotions played a mediating role in the relationship between the block variable (mindfulness and psychological capital) and mental health, and the indirect effect was 0.131.

Conclusions: This study expanded the research on the effects of mindfulness and psychological capital in improving mental health as well as the conflict between the two variables related to mental health by employing a new analytical technique among breast cancer patients.