CLOCK and major depressive disorder: To investigate the effects of a depression-like phenotype on the diurnal pattern of core clock gene expression in the mPFC, mice were subjected to the chronic behavioral despair paradigm (CDM), a mouse model of depression in which passive immobility and anhedonia (Supplementary Fig. 1a) are induced by daily 10 min swim sessions for 5 consecutive days (induction phase)13,15,26–28.