Mood and Anxiety Disorders

Mood and anxiety disorders are chronic, disabling conditions that impose enormous costs on both individuals and society at large [1–5]. These disorders are the most frequent diagnosed neuropsychiatric diseases in Western countries. According to a recent 3-year multimethod study covering 30 European countries and a population of 514 million people, anxiety and mood disorders had the highest 12-month prevalence estimates (total 14 and 6.9%, respectively) compared with all other psychiatric conditions [2]. Although there are many treatment options available for these disorders, drug discovery research in this area is still very active, with the objective of finding alternative, better tolerated, and more effective pharmacological treatments for anxiety and mood disorders. The reliance on animal models of these conditions is crucial to find new treatments. Preclinical research has devised numerous ways to test for anxiety and mood, with well over 100 tests and models by recent counts [6]. The specifics of these tests have been described in many comprehensive reviews on this topic [6–9] and we will only briefly introduce the most frequently used ones here to illustrate the strengths and weaknesses of current approaches in general. One general consideration from the outset is validity. The validity of a test for anxiety/mood in an animal rests on three criteria: face validity (Does it measure something analogous to one or more human anxiety/mood symptoms?), predictive validity (Is it reliably sensitive to clinically efficacious anxiolytics/antidepressants?), and construct validity (Does it involve some of the same pathophysiological mechanisms found in human anxiety/mood disorders?) [10]. None of the available tests or models of anxiety or mood can be said to unequivocally meet these criteria. 193