Development and Application of Accurate Detection Technology Based on Multimodal Data of Breast Cancer Comobid Depression

Inclusion Criteria: * Pathologically confirmed primary breast cancer; Aged 18-80 years; No prior history of malignancy other than breast cancer; Awareness of their breast cancer diagnosis; Karnofsky Performance Status (KPS) score \>70; Willing to provide blood, fecal, and saliva samples with signed informed consent. Exclusion Criteria: * Physician-diagnosed mental disorders before or after breast cancer diagnosis; Severe chronic somatic diseases (e.g., central nervous system disorders, severe head trauma, substance abuse/dependence, intellectual disability, diabetes, gynecological diseases, cardiovascular diseases, thyroid disorders, etc.); Presence of two or more primary malignancies of different tissue origins; Central nervous system (CNS) metastasis of breast cancer; Clinically diagnosed digestive system diseases (e.g., enteritis, gastritis); Use of antidepressant or anxiolytic therapy during the study; Use of medications that alter gut function or metabolism during the study; Pregnant or lactating women; Radiotherapy or chemotherapy within the past 21 days; Use of antibiotics, probiotics, prebiotics, or synbiotics within 3 months prior to the study; Other reasons deemed unsuitable for participation by investigators.