Further support for a role of molecular clocks in mood disorders comes from human postmortem brain analyses which show significant alterations in the diurnal variation of the circadian clock genes in extra-SCN brain regions, including the NAc, amygdala, prefrontal cortex (PFC) and hippocampus in patients diagnosed with MDD (Li J. Z. et al., 2013). Here, CLOCK is linked to major depressive disorder.