SSRI treatment altered RBC parameters and WBC parameters in adolescents with MDD but not platelets.

The monocyte percentage and MLR tended to be more affected by SSRI treatment than the NLR or PLR.

RBC parameters and inflammatory ratios in responses to SSRI treatment differed between responders and nonresponders.

Higher platelet count at baseline is associated with nonresponse to SSRI treatment in MDD.

Neutrophil–to–lymphocyte ratio (NLR), platelet–to–lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) are novel biomarkers of systemic inflammation in depression. This study aims to examines the impact of selective serotonin reuptake inhibitor (SSRI) treatment on complete blood count (CBC) parameters and inflammatory ratios in major depressive disorder (MDD). CBC parameters and inflammatory ratios were examined in a total of 45 drug-naive adolescents with MDD and were compared before and after SSRI treatment for 12 weeks and between responders and nonresponders. Following SSRI treatment in MDD, the red blood cell (RBC) count, hematocrit, and red cell distribution width (RDW) significantly increased. Hemoglobin tended to increase. The MCV, MCH, and MCHC values decreased significantly. White blood cell count, neutrophil percentage, monocyte count, and monocyte and basophil percentages decreased significantly. The percentage of lymphocytes significantly increased. The MLR decreased, whereas the NLR tended to decrease. Platelet count and PLR did not change significantly. A higher platelet count at baseline has been associated with non-response to SSRI treatment in patients with MDD. SSRI treatment increased RBC count, hematocrit, RDW, and lymphocyte percentage, and reduced MLR, and neutrophil and monocyte percentages in responders MDD. We suggest higher platelet counts at baseline as a potential predictor of nonresponders.

Antidepressants

Depression

Monocyte–to–lymphocyte ratio (MLR)

Neutrophil–to–lymphocyte ratio (NLR)

Platelet–to–lymphocyte ratio (PLR)

Selective serotonin reuptake inhibitor (SSRI) treatment

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