Trauma, Chronic Stress, and Breast Cancer Risk in Women: A Review of Potential Biological Pathways

Breast cancer remains the most commonly diagnosed cancer among women worldwide and continues to represent a major challenge for healthcare systems despite significant advances in screening, diagnosis, and treatment. While established risk factors such as age, genetic susceptibility, hormonal influences, reproductive history, lifestyle factors, and environmental exposures explain a substantial proportion of breast cancer cases, they do not fully account for the variability in disease occurrence. Increasing attention has therefore been directed toward psychosocial determinants of health, particularly the long-term biological consequences of trauma and chronic stress. This review critically examines current evidence regarding the relationship between trauma, chronic stress, and breast cancer risk in women. Drawing upon literature from psychoneuroimmunology, endocrinology, oncology, neuroscience, and women's health, the review explores the biological pathways through which traumatic experiences may become biologically embedded across the life course. Particular attention is given to dysregulation of the hypothalamic-pituitary-adrenal axis, chronic inflammation, immune dysfunction, oxidative stress, epigenetic modifications, and behavioural adaptations that may collectively influence the physiological environment associated with breast cancer susceptibility. The review also considers women's unique exposure to traumatic experiences, including adverse childhood experiences, intimate partner violence, caregiving burden, financial adversity, and gender-based violence, all of which may contribute to cumulative physiological stress. Importantly, the available evidence does not support a direct causal relationship between trauma and breast cancer. Rather, it suggests that chronic stress associated with traumatic experiences may interact with established genetic, hormonal, environmental, and behavioural risk factors through complex and interconnected biological mechanisms. By integrating evidence across multiple disciplines, this review highlights the importance of adopting a life course perspective when examining breast cancer risk in women. It identifies important gaps in the current literature and outlines priorities for future research, including longitudinal investigations, mechanistic studies, and the integration of trauma-informed approaches within women's health and cancer prevention. A deeper understanding of these pathways has the potential to inform more comprehensive models of disease prevention, early intervention, and patient-centred care.