“…For example, decreased red blood cell (RBC) SOD activity was reported in patients diagnosed with recurrent depressive disorder (Rybka et al, 2013), lowered serum SOD levels in patients with major depression (Herken et al, 2007, Stefanescu andCiobica, 2012), and even greater reductions in serum SOD in patients with recurrent depression, compared to a first episode group (Stefanescu and Ciobica, 2012). However, in other studies increased RBC SOD in depressed patients were found (Bilici et al, 2001, Galecki et al, 2009a, Kodydkova et al, 2009, Kotan et al, 2011, Sarandol et al, 2007, and serum SOD was positively associated with increasing severity of depression (Khanzode et al, 2003). Reasons for these inconsistent findings are not clear, although may be related to variable collection protocols, analysis methods and whether RBC or serum was analysed (e.g., RBC levels were elevated in four out of five studies reviewed, while serum levels were lower in two out of three studies reviewed).…”