Evaluation of neutrophil-to-lymphocyte, platelet-to-lymphocyte, monocyte-to-lymphocyte ratios, mean platelet volume, and systemic immune inflammation indices in attention-deficit/hyperactivity disorder

Systemic inflammation has been increasingly recognized as a significant factor in the pathophysiology of Attention-Deficit/Hyperactivity Disorder (ADHD). However, studies investigating the utility of peripheral inflammatory biomarkers, such as those derived from complete blood counts, remain limited. This study aims to compare children diagnosed with ADHD to healthy controls in terms of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), mean platelet volume (MPV), systemic immune inflammation index (SII), systemic inflammation response index (SIRI), and aggregate index of systemic inflammation (AISI). Another aim of the study was to investigate these values based on the predominant clinical presentations and symptom severity in children with ADHD. A retrospective analysis was conducted on medical records of 154 children and adolescents diagnosed with ADHD, and 77 healthy controls, who presented to the Child and Adolescent Psychiatry Clinic of Suleyman Demirel University Hospital from 2019-2023. Inflammatory markers were obtained from complete blood count tests. Clinical data, including results from the Turgay DSM-IV Based Child and Adolescent Disruptive Behavior Disorders Screening and Rating Scale, the Conners' Parent Rating Scale, the Strengths and Difficulties Questionnaire, and the Revised Child Anxiety and Depression Scale, were also analyzed. There were no statistically significant differences in NLR, MLR, PLR, MPV, SII, SIRI, or AISI between children with ADHD and healthy controls. Moreover, no significant differences were found in inflammatory marker levels between children with predominantly inattentive and combined ADHD presentations. A weak but statistically significant correlation was identified between MPV and attention-deficit symptom severity, as well as between PLR and hyperactivity/impulsivity symptom severity. Additionally, NLR showed a weak positive correlation with scores on scales for major depressive disorder and generalized anxiety disorder. This study is the first to evaluate novel inflammatory indices, such as SIRI and AISI, in the context of ADHD. Although no significant differences were observed in these markers between ADHD patients and healthy controls, it should be considered that these results may be influenced by several confounding factors. Consequently, there is a need for longitudinal studies with larger sample sizes to further elucidate these associations.