Depression: What is the Role of Physiological Dysregulation and Circadian Disruption?

Douglas Watt and Jaak Panksepp have provided an excellent and wide-ranging review that analyzes what is missing in current theories of the etiology of depression, and they effectively present the notion that depression is a state that is rooted in misuse of an adaptive and normal response—namely, the termination of separation distress. They suggest that multiple neural systems react in order to suppress the distressful feelings associated with separation of the infant from the mother. In adulthood, according to their view, this same system acts to prevent an organism from continuously seeking out a goal that is unreachable and thus prevents a pointless waste of resources. In their view, depression can be thought of as the inappropriate engaging of this system. Thus, improper activation of the neural systems that terminate separation distress, or perhaps an incomplete shutdown of these systems, can lead to a pathological impairment of normal behavior, resulting in the individual withdrawing.

Potentially even more important is their view that depression involves the malfunction and desynchronization of multiple interacting neural and neurochemical systems. We propose that separation distress is an example of a more global dysregulation of the organism's neural and systemic ability to adapt, based on the concept of allostasis and the build-up of allostatic overload. In particular, the dysregulation of circadian rhythms can lead to an allostatic state, resulting in the dysfunction of many of the same systems that Watt & Panksepp highlight in their more specific focus on separation distress.

Adaptation is key to survival. This is true for the lowliest unicellular organism, all the way through the phylogenetic tree to humans. Selective pressures have resulted in organisms that possess exquisitely tuned systems that regulate the functions of life. In some instances, these systems are relatively “simple” biochemical cascades (e.g. th