TNF and attention deficit-hyperactivity disorder: Yet, IL‐1β, IL‐2, IFN‐ɣ and TNF‐α, pro‐inflammatory cytokines produced by Th1 cells as well as other immune cells such as other lymphocytes and macrophages, have been linked to ADHD or ADHD symptoms in previous studies (Anand et al., 2017; Cortese et al., 2019; Leffa et al., 2018).