Figure 2 suggests that SIRT1 mRNA levels of schizophrenia patients with depression were significantly lower than those of schizophrenia without depression (P < 0.01). Consistent with our previously published results (Fang et al., 2019), the present study also suggested that the CDSS score was negatively correlated with SIRT1 mRNA levels (r = −0.328, P < 0.01). The gene discussed is SIRT1; the disease is major depressive disorder.