Blood Count Parameters as Inflammation Indicators in Children and Adolescents Diagnosed with Depressive Disorder

There is increasing evidence that immunological and inflammatory dysfunctions play an essential role in the initiation and progression of major psychiatric disorders. Neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and mean platelet volume can be used as markers of systemic inflammation in different diseases. We aimed to investigate these blood count parameters in children and adolescents diagnosed with major depressive disorder.

Designed as a case-control study, our sample consisted of patients aged 9-16 years referred to Child and Adolescent Psychiatry and pediatrics outpatient clinics for the first time and diagnosed with major depressive disorder according to Diagnostic and Statistical Manual of Mental Disorders, 5th edition diagnostic criteria, and healthy children and adolescents matched at a ratio of 1 to 2. Data of 58 cases and 90 healthy controls evaluated between 01.07.2019 and 01.07.2020 were included.

Platelet-to-lymphocyte ratio values were significantly higher in the case group. No significant difference was found between patient and control groups regarding other blood count parameters. When depression group was compared in terms of all parameters as those who committed suicide and those did not, significant difference was found between the 3 groups in terms of platelet-to-lymphocyte ratio values. The intergroup difference in platelet-to-lymphocyte ratio was found between the depression group without suicide and the control group. No significant relationship was found between other parameters and Children's Depression Inventory Scale scores. We determined a cut-off value of 112.5 for platelet-to-lymphocyte ratio (with sensitivity of 70% and specificity of 63%).

Platelet-to-lymphocyte ratio might be an important parameter in the clinical follow-up of major depressive disorder.