This “integrative single-case study” investigated the bidirectional cause and effect relations between various emotional states (i.e., mood, irritation, mental activity) and urinary IL-6 levels in a 49-year-old female breast cancer survivor (woman) under conditions of “life as it is lived.” During a period of 28 days, the patient collected her entire urine in 12-h intervals for IL-6 measurement and completed each morning and evening a list of adjectives regarding mood, irritation, and mental activity (55 measurements in total). Here, IL6 is linked to breast cancer.