SMAD3 and major depressive disorder: In addition, behavioral results showed that compared with that of the PTSD group, in situ, stereotactic injection of Smad3 protein (sf9, His‐GST) into the prefrontal cortex before PTSD modeling significantly aggravated PTSD‐like depression and fear symptoms in mice, and the difference was not statistically different from that in mice of TBI+PTSD group (Figure S5B,C, Supporting Information).