We have observed perturbance of circadian rhythms in the behaviors (such as the locomotor activity and sleep–wake cycle) and clock gene expression in mice with delirium‐like syndrome, consistent with our and previous clinical observations that patients with delirium show disrupted circadian rhythms (Figure S3E/F).[22, 23, 24, 25, 26] Importantly, we show that mice with circadian disruption are delirious prone with aggravated cognitive impairment, supporting involvement of clock dysfunction in the pathogenesis of delirium. This evidence concerns the gene CLOCK and Cognitive impairment.