Stress and risk of breast cancer; findings from a large population-based incident case-control study

Purpose The relationship between stress and breast cancer (BC) remains a topic of debate. We investigated the association between stress experienced within the past year and the risk of BC. Methods Population-based incident case-control study of 600 newly diagnosed BC cases and 600 population controls (18–75 years) recruited in Isfahan, Iran between 2021–2023. Logistic regression model with short-term stress as main exposure was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) after adjusting for confounders. Stratified analysis was done based on menopausal status. Results One-year stress level was significantly associated with BC risk, and the odds of BC were elevated in those with high stress levels in unadjusted (OR = 3.10, 95%Cl: 2.45–3.92) and in fully adjusted (OR = 3.38; 95%CI (2.56, 4.47)) models. Menopausal status was found to be potential effect modifiers of the stress-breast cancer relationship. Conclusion Despite the inherent limitations of case-control studies, this population-based incident case-control study showed that high stress experienced within the past year is a significant risk factor for BC, particularly among pre-menopausal women. These findings highlight the potential role of stress in BC etiology.