As for ADHD, ADHD was nominally associated with decreased albumin (beta = −0.019, 95% CI ranges from −0.027 to −0.011, p = 0.015; p of egger intercept = 0.320), decreased bilirubin (beta = −0.042, 95% CI ranges from −0.011 to −0.063, p = 0.046; p of egger intercept = 0.685; this causal effect disappeared in weighted median method), and decreased CAT (beta = −0.098, 95% CI ranges from −0.142 to −0.055, p = 0.024; p of egger intercept = 0.101; this causal effect disappeared in weighted median method). The gene discussed is CAT; the disease is attention deficit-hyperactivity disorder.