[What clinicians expect from animal models of depression]

In depression research, animal models are essential for better understanding of biological mechanisms, development of new agents, and showing evidence on various theories. Given the emotional feature of the disorder, people have debated, even revolted, on applying animal models to human studies. However, this logic is counter-arguable by noting the commonality of biological changes (e.g., behavioral disorder, environment maladjustment, and stress vulnerability) between human and experimental animals; moreover, genetic studies suggest further similarities. However, current animal models are insufficient to express the full dimension of mood disorders. The model concepts are often in a narrow context of antidepressant responses. The models consider stress models as equivalents of depression models. This hypothesis, however, has limitations in differentiating anxiety- and stress-related models from depression models. The models tend to focus on the depressive, but not manic, state; it is thereby a challenge to replicate depressive and manic phases in animals. The models do not have a standpoint of depressive disorder from cognitive aspects, and are unable to replicate mood disorder subtypes, such as atypical depression, dysthymia, bipolar disorder, and seasonal affective disorder. From a clinical perspective, models of treatment-resistant depression would eventually be of large benefit to enhance treatment outcomes in clinical settings.