We performed immunohistochemistry on a series of 22 paraffin sections from the hippocampal formation taken from a total of 20 brains from all four groups under study (schizophrenia (n= 9), major depression (n = 3), bipolar disorder (n = 3), and control (n = 5)), using the antibody (Anti-Oct-6 (N)) and staining procedure as in the previous study [6]. This evidence concerns the gene POU3F1 and major depressive disorder.