The illness representations–physical well-being interplay over time in breast cancer patients.

Many studies have shown the prospective relation of illness representations to breast cancer patients' well-being. Still, very few have examined their bidirectional relationship over time. Here, the long-term mutual effects between physical well-being and illness representations were examined at the within-person level. Female patients with breast cancer were enrolled in the study 2-5 weeks after the surgery or biopsy (baseline N = 706; Mage = 54.93). Several illness representations (i.e., illness consequences, timeline, personal control, and emotional representations) and physical well-being (i.e., general physical functioning and specific breast and arm symptoms) were assessed at 6, 12, and 18 months after patients' inclusion in the study (years of data collection: 2019-2021). Two random-intercept cross-lagged panel models were used to examine whether intrapersonal changes in the two variables predicted each other across time. The findings showed strong general relations between illness representations and physical well-being at the between-person level. However, only changes in timeline and emotional representations predicted intrapersonal subsequent changes in physical functioning and arm and breast symptoms, respectively. No other cross-lagged effects were found. While illness representations are significantly associated with physical well-being at the between-person level, their impact significantly varies at the within-person level. The findings reflect the complex relationships between these factors in patients with breast cancer and point to the need for new theoretical approaches to better depict their long-term intrapersonal interplay. (PsycInfo Database Record (c) 2025 APA, all rights reserved).