The word “depression” has become a common everyday word. We hear the term “depression” so often today that it is even used in the context of jokes. For example, you may hear someone say, "My favorite show is over, now I have nothing to watch, I'm so depressed." Obviously, this person is not depressed, but we have come to overuse it in our expressions, to the point that it takes away from the seriousness of this disorder. Major depressive disorder is a mood disorder characterized by at least two weeks of depressed mood or loss of interest in almost all activities, accompanied by problems sleeping or eating, loss of energy and a feeling of hopelessness (Kosslyn, Rosenberg, 2006). This mood disorder is characterized by depressed mood, a lack of interest in normally enjoyed activities, and a feeling of worthlessness. Over the course of two weeks, a person with major depressive disorder may experience symptoms such as significant weight loss, daily insomnia or hypersomnia, loss of energy, decreased ability thinking or concentration and recurring thoughts of death or suicide (Kosslyn, Rosenberg, 2006). Major depressive disorder is not a passive feeling of unhappiness, nor is it a feeling of grief and sadness over the stressors of daily life. Feelings such as sadness and grief are normal reactions to life, and over time these feelings will go away and people will move on with their lives. On the other hand, without medical care, major depressive disorder persists and does not disappear over time. In most cases, major depressive disorder is a recurring illness; meaning that a person who has been depressed once in their life and recovered from it is likely to experience one or more episodes of depression in the future (Kosslyn, Rosenberg...... middle of paper. ..... Essentially, the line between psychology and neurology is blurred when it comes to depression. The feedback loop involved in this disorder cuts across levels between chemical, structural, and psychological domains, thereby creating depression. . very difficult to understand and cure. Works Cited Klosko, J., Sanderson, W. 2000. Cognitive and Behavioral Treatment of Depression Northvale, New Jersey. (. 2006). Psychology in Context. Boston, MA: Allyn & Bacon, Inc. Suri, D., Vaidya, V. 2012. Glucocorticoid regulation of brain-derived neurotrophic factor: relevance to structural and functional plasticity. hippocampus: 196-213. World Health Organization. (2004). The global burden of disease. Geneva, Switzerland.