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…