Symptoms of depression and anxiety as predictors of physical functioning in breast cancer patients. A prospective study using path analysis

BACKGROUND: Although symptoms of depression and anxiety are linked to health-related quality of life (HRQoL), the nature of this relationship remained unclear. We therefore aimed to examine, in a prospective study, both possible directions of impact in this relationship. To avoid conceptual and measurement overlap between depressive and anxiety symptoms, on the one hand, and HRQoL, on the other hand, we focused on the physical functioning component of HRQoL.

MATERIAL AND METHODS: We conducted a secondary analysis of a prospective cohort study with 436 female breast cancer patients (mean age 51 years). Both at baseline and after 12 months, we measured symptoms of depression and anxiety with the four-item Patient Heath Questionnaire (PHQ-4) and physical functioning with the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). Using path analysis, we estimated (1) the predictive value of symptoms of depression/anxiety for subsequent physical functioning and (2) the predictive value of physical functioning for subsequent symptoms of depression/anxiety, in the same model.

RESULTS: Baseline symptoms of depression/anxiety predicted 1-year levels of physical functioning (depression: standardized β =  -.09, p = .024; anxiety: standardized β =  -.10, p = .009), while the reciprocal paths linking baseline physical functioning to subsequent depressive and anxiety symptoms were not significant, adjusting for the baseline scores of all outcome variables.

CONCLUSIONS: Depressive and anxiety symptoms were predictors of the physical functioning component of HRQoL. Thus, if this relation is causal, treating breast cancer patients' depressive and anxiety symptoms may have a favorable impact on their self-reported physical functioning.