Conceptual Challenges of a Tentative Model of Stress-Induced Depression

The concept of a stress-induced depression has recently been proposed in light of new findings from animal and human studies. Depression associated with stress involves a number of body systems such as the neuroendocrine and neurotransmitter system and the immune system including cytokines and the dysregulation of the HPA axis interacting in complex pathways. However, numerous research challenges present when addressing a tentative concept of stress-induced depression. One of them is the requirement to establish a causative relationship between stressful environmental factors and stress-related neurochemical and genetic pathways in a complex model of interaction using valid and etiological relevant animal models. Another challenge is the establishment of animal models compatible with the concept of stress-induced depression; however, chronic mild and social stress models are promising models for the study of stressfully perceived environmental events assembling stressors relevant in depression. Moreover, the consideration of individual psychological ‘‘neurotic’’ factors presents another major challenge in animal and human models of stress-induced depression. In addition, the study of translational implications is needed to enhance research into the validity and relevance of a tentative concept of stress-induced depression.