Exploring the complex relationship between attention deficit hyperactivity disorder and the immune system: A...

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental condition that can be accompanied by alterations in immune markers. However, the intricate nature of the association between ADHD and immune markers remains insufficiently elucidated. To explore the currently ambiguous causal relationship between ADHD and the immune system, we performed a bidirectional Mendelian randomization (MR) analysis of immune cell traits and ADHD under the randomized inverse variance weighting (IVW) method based on genome-wide association study (GWAS) summary data. We found ADHD increased the level of 3 immune cell traits including myeloid dendritic cells (β = 0.28, P = 0.008), monocyte (β = 0.25, P = 0.024) and granulocyte (β = 0.2, P = 0.042). We also identified 1 trait which belongs to B cell panel was a risk factor (odds ratio (OR) = 1.07, P = 0.001) for ADHD onset. Other 5 traits including CD14+ monocyte (OR = 0.98, P = 0.002), immature myeloid-derived suppressor cells (MDSC) (OR = 0.98, P = 0.003), monocyte MDSC (OR = 0.95, P = 0.005), CD33br HLA DR+ (OR = 0.97, P = 0.021) and basophil (OR = 0.96, P = 0.022) were protective factors for ADHD. Here we identified a range of causal relationships extending from ADHD to immune cell traits, underscoring the complex interaction patterns between ADHD and the immune system. Enhanced interventions for protective and risk factors may be beneficial in the prevention and treatment of ADHD.