Depression in breast cancer patients: Immunopathogenesis and immunotherapy.

Depression is a common and recurrent mental illness with a complicated etiology, but the specific pathogenesis is not clear. Breast cancer increases susceptibility to depression, which leads to a poor prognosis. Rapid advances in the understanding of tumor immunology and neuroimmunology have provided new evidence for the pathogenesis of depression. Dysfunction of immune cells and cytokines cause depression by affecting tryptophan metabolism, serotonin levels, and blood-brain barrier permeability. Dysregulation of cytokines or intestinal flora may be shared between patients with depression and breast cancer. This review presents an overview of immune dysregulation in breast cancer patients with depression and proposes future alternative research directions and interventions.