Depression

Mood disorders affect ~20% of the American population over their lifetime and yearly prevalence rates are close to 10%, including 6.7% for major depressive disorder (MDD). Moreover, depression is the leading cause of disability worldwide. MDD is characterized by symptoms of emotional, motivational, cognitive and physiological domains making it a complex disease to treat. Furthermore, depression is often associated with chronic illnesses or other mood disorders such as co-morbid anxiety, all of which can be predictors of poor response to antidepressant treatments. In fact, it is estimated that only 50% of depressed patients are responsive to currently available antidepressant treatments. Modeling human depression in animals is challenging considering the subjective nature of the multiple psychological and physiological symptoms and the lack of objective biomarkers. Validity of an animal model is generally evaluated with the following criteria: 1) manifestation of symptoms are reasonably analogous to the human disorder, 2) behavioral changes can be monitored objectively and 3) behavior changes can be reversed with therapeutically effective antidepressant treatments.