Catalase activity is presented in Figure 2B, demonstrating a lower catalase activity in the smoker group (224.56±37.7 k/mL) and in patients with opioid use disorder (216.82±33.4 k/mL) compared to the non-smoker (274.22±31.6 k/mL, p<0.05, Figure 2B) group. This evidence concerns the gene CAT and opioid use disorder.