GSTM1 and attention deficit-hyperactivity disorder: Oxy-Hb signal in control subjects was significantly higher than in post-placebo ADHD subjects (independent two-sample t-test, thresholded at p < 0.05 Bonferroni-corrected, Cohen's d = 1.176), while there was no significant difference between control subjects and post-ATX-ADHD subjects (independent two-sample t-test, thresholded at p = 0.430, Cohen's d = 0.283).