Abstract
Objectives: This study aimed to assess whether race modifies irritability and immunological inflammation, and their interaction to worsen depression during chemotherapy. Methods: 25 African American and 19 White nonmetastasized breast cancer patients were assessed on irritability, inflammation biomarker (hsCRP and IL-6), and depression at baseline (T 1 ) and after 3 months of chemotherapy (T 2 ). Wilcoxon rank sum test was performed to compare racial groups on these study variables. Generalized estimating equations (GEE) regression models for repeated measures were computed, using the severity of depression as the dependent variable, race, an inflammation biomarker (hsCRP or IL-6), irritability, interactions of these variables, and time as independent variables, controlling for age, baseline depression severity level and its racial difference. Results: The African American cancer patients had significantly higher levels of hsCRP (p = .040) and IL-6 (p = .018) than the White patients at T 2, without a significant baseline difference. In both regression models, the African American patients experiencing greater irritability reported significantly more severe depression at T 2 (p = .0002; .0048). In the regression model containing hsCRP, a negative interaction between irritability and hsCRP level was significantly associated with more severe depression at T 2 (p < .0001). In the regression model containing IL- 6, the African American patients (p = .03), most of whom had higher IL-6 (p < .0001), reported significantly more severe depression at T 2 , while White patients who had higher IL-6 levels also had more severe depression at T 2 (p = .016). Conclusion: Association between irritability and depression was significantly stronger for the African American patients than the White patients in this study, and the level of hsCRP influenced irritability and its association with depression. Identification of contributors to irritability, particularly for African Americans, is important for reducing irritability and depression in cancer patients undergoing chemotherapy. Moreover, the White cancer patients in the study who experienced higher IL-6 levels during chemotherapy were also at a higher risk of worsening depression and required medical attention.