What should animal models of depression model?

Frazer, A. & Morilak, D.A. (2005). What should animal models of depression model?, Neuroscience and Biobehavioral Reviews, Volume 29, 515-523.

Experimentation with animals offers researchers great liberties in studying a disorder. However, proper animal models must first be developed and agreed upon. Animals models for testing fear, as an example, are made possible because fear is an emotion that is conservative across species; that is, fight, flight, or freeze responses appear consistently. However, researchers have struggled with defining models for other disorders which lack such obvious behavioral patterns. Depression is such a disorder. This article asks the question, "What should we be attempting to model with animal models of depression?".

Major depressive disorder (MDD) is a syndrome with a constellation of behavioral features. Making matters worse, the etiology of MDD remains unknown. That MDD is a diagnostic construct and is comorbid with many other psychiatric diagnoses also does not help. This article suggests placing an emphasis on modeling specific behavioral dimensions (or characteristics) that are dysregulated in depression, rather than trying to recreate or mimic the entire spectrum of symptoms of depression or even specific symptoms associated with it. This will be more conducive to experimentation and to understanding the regulatory mechanisms by which antidepressant drugs alleviate such a cluster of symptoms. Three dimensions were put forth in the paper: negative affect, loss of positive affect, and physiological hyperarousal.