GFI1 and attention deficit-hyperactivity disorder: After adjustment for potential covariates, including maternal smoking exposure during pregnancy, a one-unit percent (%) increase in DNA methylation rates on a region of ESR1 (OR, 0.93; 95% CI 0.91–0.95) and GFI1 (OR, 0.94; 95% CI 0.92–0.97) regions was associated with significantly lower odds of ADHD symptoms.