CD40 and attention deficit-hyperactivity disorder: A total of six inflammatory cytokines were associated with ADHD, of which AXIN1 (IVW: OR = 1.141, 95% CI: 1.004–1.297, p= 0.044; Figure S33), CCL11 (IVW: OR = 1.07, 95% CI: 1.008–1.136, p= 0.025; Figure S34), FGF‐19 (IVW: OR = 1.077, 95% CI: 1.009–1.148, p= 0.025; Figure S36), and hGDNF (IVW: OR = 1.084, 95% CI: 1.014–1.159, p= 0.019; Figure S37) were risk factors for ADHD, whereas CD40 (IVW: OR = 0.933, 95% CI: 0.893–0.975, p= 0.002; Figure S35) and NT‐3 (IVW: OR = 0.875, 95% CI: 0.782–0.979, p= 0.019; Figure S38) were protective against ADHD.