Depression can be both normal and abnormal, and the balance of its expression determines the behavioral outcome/diagnosis. It is a complex pathophysiology based on a heterogeneous syndrome whose etiology is diverse as well. Within the context of a central nervous system, the nervous system blueprint can be found in single cells (sensory, motor, and integrative processes). These consolidated functions provide for novel coping strategies for survival. The maintenance and evolvement of this system into a central nervous system is based on conserving these functions, including chemical messengers and functionality in having specific cells medi-ate these primordial functions. Additionally, this neural coping strategy provides advantages for DNA. Thus, with different neural cells at work, pathways/networks would evolve, producing more complex behaviors and become a very critical phenomenon for future advances. This evolvement has taken over 1 billion years to de-velop. In so doing, as with any new programming (e.g., cognition), errors will occur. Given the widespread qual-ities of depression, it is surmised that this abnormality, and other psychiatric disorders, may emerge due to in-herent neural weaknesses related to cognition being a recent evolutionary development.

Keywords: Central Nervous System - physiopathology, Biological Evolution, Cognition - physiology, Cognition Disorders - physiopathology, Depression - physiopathology