CAT and anxiety disorder: Further, studies in populations with anxiety disorders have demonstrated increased activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), xanthine oxidase, glutathione reductase (GSR), and glutathione peroxidase (Kuloglu et al. 2002; Tezcan et al. 2003; Herken et al. 2006; Atmaca et al. 2008; Ozdemir et al. 2009).