CLDN5 and bipolar disorder: Levels of claudin-5 positively correlated with the age of onset of bipolar disorder in the hippocampus white matter (r = 0.6442, P = 0.044 (not significant with FDR correction)) (Fig. 5A, C), grey matter (r = 0.586, *P = 0.030) (Fig. 5A) and orbitofrontal white matter (r = 0.6172, *P = 0.0162) (Fig. 5A, D).