In our previous study, we demonstrated that KD of Per1 in the hippocampal CA1 region resulted in enhanced depression-like behaviors, such as a reduction in sucrose preference and prolonged immobility time in the FST, while knockdown of Per2 produced the opposite effect in the FST (Wang et al., BioRxiv, 2021) [66]. This evidence concerns the gene PER1 and major depressive disorder.