In bipolar disorder, the activities of superoxide dismutases (SODs) and catalase (CAT) have been found to be decreased in the blood (Ranjekar et al., 2003), while the activity of glutathione peroxidases (GPXs) has been shown to be comparable between bipolar patients and healthy individuals (Kuloglu et al., 2002c; Ranjekar et al., 2003). Here, CAT is linked to bipolar disorder.