Potential usefulness of complete blood count parameters and inflammatory ratios as simple biomarkers of depression and suicide risk in drug-naive, adolescents with major depressive disorder

We determined whether an elevated neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) were associated with depression in major depressive disorder (MDD), or suicide risk in MDD patients. A total of 137 adolescents with MDD who were antidepressant-naive and 56 healthy controls (HC) were included. Recent suicidal behaviors were assessed. The NLR, PLR, and MLR were calculated from parameters obtained from a routine complete blood cell count parameters and compared between the MDD subgroups and HC. Cohen's d was calculated as a measure of effect size. The linear relationship between biomarkers with depression severity or suicidality severity was also analysed. Changes in CBC parameters and inflammatory ratios appeared to be more closely related to the suicidality severity than depressive severity. As compared with HC, the WBC count, neutrophil percentage, platelet count, NLR, and PLR were higher in MDD, whereas the lymphocyte percentage was lower. As compared to non-suicidal ideation (non-SI) MDD and HC, the lymphocyte percentage was decreased in MDD with suicidal attempts (SA), whereas monocyte count and MLR were increased. Suicidal attempts in MDD patients were associated with the lower lymphocytes percentage, as well as the elevated monocyte count and MLR.