Furthermore, patients with MDD show significantly lower SIRT1 mRNA levels in peripheral white blood cells in depressive states whereas this reduction in SIRT1 mRNA is not observed in MDD patients in remissive state, implying that SIRT1 in peripheral white blood cells could be utilized as a potential state-dependent biomarker for MDD (Abe et al., 2011). The gene discussed is SIRT1; the disease is major depressive disorder.