Peripheral Inflammation In Adult ADHD: Sex Differences And Hematological Markers

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by impairments that persist into adulthood. Despite advancements in our understanding of ADHD, the factors influencing its course remain unclear. The inflammatory hypothesis suggests that immune dysregulation may contribute to ADHD pathophysiology. However, research examining inflammation in adult ADHD is limited. This cross-sectional study aimed to compare complete blood count (CBC) parameters and derived inflammatory indices between adult patients with ADHD and healthy controls, with particular attention to sex differences. The study included 72 drug-free adults with ADHD (aged 18-38 years) diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) and 72 age- and sex-matched healthy controls. CBC parameters and inflammatory indices, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), basophil-to-lymphocyte ratio (BLR), mean platelet volume (MPV), platelet distribution width (PDW), systemic immune-inflammatory index (SII), and pan-immune inflammatory value (PIV), were compared between the groups. Monocyte counts were significantly higher in the ADHD group than in the control group (p = 0.019). Sex-specific analysis revealed no significant differences in inflammatory parameters among females. However, male patients with ADHD showed significantly elevated leukocyte, neutrophil, and monocyte counts compared to male controls (p = 0.031, p = 0.049, and p = 0.038, respectively). These findings suggest that elevated monocyte levels, indicative of chronic inflammation, may have diagnostic implications in adult ADHD, particularly among males. These findings underscore the necessity to incorporate sex-specific biological mechanisms when investigating and developing therapeutic strategies for ADHD.