CLDN-5, PUM1 and PUM2 mRNA levels in the post-mortem hippocampal sections of patients with bipolar (BP), schizophrenia (SCZ) and major depressive disorders (MDD) were measured (Fig. 4a) as BBB integrity in the hippocampus is especially vulnerable to oxidative damage and other stress related stimuli [41]. Here, CLDN5 is linked to major depressive disorder.