Disrupted Circadian Rhythms, Stress, and Allostatic Load

The brain and body work together to ensure survival. Under typical conditions, the endogenous circadian (daily) clock helps predict regularly occurring events, like the day–night cycle, to build a behavioral and physiological framework that optimizes use of resources while taking advantage of environmental opportunities. On the other hand, the stress system responds to emergencies, deploying countermeasures that promote survival in the face of threat. When the stress system is engaged inappropriately or for too long, factors that help promote adaptation (allostatic mediators) can cause damage to the biological systems they are meant to protect. This allostatic load can lead to allostatic overload, where a cascading set of failures in these systems lead to pathology. Here, I discuss the interplay between the stress and circadian systems, how disruption of the circadian clock can contribute to allostatic load and overload, and the negative health consequences that this can cause.