Associations Between Hematologic Profiles and Depressive Disorder in Adolescents

Adolescent depressive disorders are common and often interfere with adolescents’ everyday functioning, school life, and social relationships. Although there is growing interest in finding objective ways to support these disorders’ clinical assessment, blood-based measures for young people have been relatively overlooked. As low-grade inflammation and changes in hematopoiesis are thought to play a role in depression, we explored whether routinely obtained hematological measures show meaningful patterns in relation to depressive symptom severity among South Korean adolescents. We retrospectively analyzed the electronic health record data of 1,074 adolescents with depressive disorders and 1,220 healthy controls aged 13–18 years. Depressive symptoms were assessed using the 17-item Hamilton Depression Rating Scale. Blood samples were obtained from routine laboratory tests, and associations between peripheral blood parameters and depressive symptoms were examined using correlation analyses and multivariable least absolute shrinkage and selection operator (LASSO) regression analysis. Compared with the control group, the depression group exhibited lower red blood cell count, hemoglobin, hematocrit, and mean corpuscular hemoglobin concentration, but higher platelet and white blood cell counts. Correlation analyses showed that greater depression severity was associated with reduced hemoglobin, hematocrit, red blood cell count, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and eosinophil levels. LASSO regression revealed that hemoglobin, hematocrit, and eosinophil counts were negatively associated with scores on the Hamilton Depression Rating Scale. Although these markers are unlikely to serve as standalone diagnostic indicators, they may offer complementary information regarding inflammatory or hematopoietic alterations in youths with depression.