Abstract—Depression has become one of the most concerning disease in the world and is projected to be the most serve global burden of disease by 2030. Its high morbidity, high relapse and high mortality features have caused millions of deaths and exerted impact on societies all over the world. Although researchers have been trying to address this problem for decades, there are still no proper solutions. This review concludes two major diagnostic systems, current progress of depression’s mechanisms, and available treatments on the market. Moreover, it specifically adds animal models and corresponding behavioral tests, and evaluates their pros and cons, aiming to help future researchers better conduct their experiments.