PDE4B and post-traumatic stress disorder: Specifically, PDE4B/Pde4b expression levels were significantly negatively correlated with PTSD reexperiencing symptoms (r = −0.46, p = 0.01; Spearman’s ρ = −0.49, p = 0.005), downregulated after fear memory retrieval in mice (FC = −1.4, p < 0.001), and lower in patients than in controls (p = 0.031) (Fig. 4B and Fig. 5A, B).