Stress is known to be one of the main causal factors of depression (Kendler, Karkowski and Prescott, 1999). It is known that major stressors in life, such as divorce or death in the family, are all related to the development of depression in people (Kendler et al., 1999). Such traumatic and sudden events can place a person under acute stress which can lead to problems such as depression. However, equally stressful for people is chronic stress: not as stressful as major stressors, but still pervasive enough in everyday life to contribute to an overall decline in positive affect. Although depression is often referred to in psychology as the “common cold,” it can still be a dangerous condition, particularly due to the increased suicidal ideation that can occur in some depressed people. For this reason, research is constantly seeking a better understanding of the condition. Because much truly experimental research on humans with depression would constitute a violation of ethics, most research in this area focuses on animals. The study conducted by Henningson et al. subject of this article used rats to study the effects of depression due to chronic stress on cognitive performance. Since it is impossible for rats to indicate in the same way as humans that they are depressed, a model to mimic the development was created and the progression was developed by researchers in the 1980s. Called the chronic mild stress model (CMS model), rats or mice are exposed to mild stressors for a number of weeks (one to seven) and their intake of a particular sucrose solution is monitored. Decreased sucrose consumption or preference is thought to reflect decreased sensitivity to rewards (Willner, 2005), a classic example of anhedonia, which is a common symptom... half of article... ion: Relation to anhedonic responses. Behavioral Brain Research, 198(1), 136-141.Kendler, K. S., Karkowski, L. M., & Prescott, C. A. (1999). Causal relationship between stressful life events and the onset of major depression. Journal of American Psychiatry, 156 (6), 837-841. Nestler, E.J., Gould, E., Manj, H., Buncan, M., Dunman, R.S., Greshenfeld, H.K., et al. (2003) Preclinical models: state of basic research in depression. Biological Psychiatry, 52(6), 503-528. Papp, M., Willner, P., & Muscat, R. (1991). An animal model of anhedonia: Attenuation of sucrose consumption and conditioning of place preference by unpredictable chronic mild stress. Psychopharmacology, 104 (3), 255-259.Willner, P. (2005). Chronic mild stress (CMS) revisited: behavioral neuro-biological consistency and concordance in the effects of CMS. Neuropsychobiology, 52 (1), 90-110.