TNF and attention deficit-hyperactivity disorder: In general, people with ADHD have altered immunological profiles, including typically higher levels of interleukin 6 (IL-6, known to influence microglia), IL-1-beta (a key proinflammatory cytokine known to influence microglia) [14], IL-1-beta (a key proinflammatory cytokine), and tumor necrosis factor (TNF) alpha (related to a weak immune response), which negatively correlate with symptom severity [17].