Another study reported that an aggregation of hyperphosphorylated tau protein appeared in the synapse of the hippocampus from C57BL/6 mice exposed to chronic unpredictable mild stress, and this effect could be reversed by ketamine, which is an N‐methyl‐D‐aspartate (NMDA) receptor antagonist that produces a rapid, long‐lasting, and potent antidepressant effect in patients suffering from major depression (Wen et al., 2019). This evidence concerns the gene MAPT and major depressive disorder.