According to the World Health Organization (WHO), “depression” is a common mental disorder with symptoms of sadness, loss of interest, guilt or self-deprecation. These characteristics tend to affect one’s sleep and appetite. A long period of time in the depressed condition can evolve from a subclinical depression to a state of clinical depression which will seriously affect one’s daily activities. Furthermore, some cases of depression would result in suicidal tendencies. According to Chang Gung Memorial Hospital in Linkou, the report on“depression” shows that in Taiwan the population suffering from depression is increasing yearly, indicating that approximately 13-20% of adults have depression-related symptoms. Furthermore, the data shows that depressioncaused suicide success rates are 15%, which involve mostly male patients. Thus, depression is indeed a serious topic of the modern society that should not be overlooked. Is “depression” just a modern issue of concern? In this research, I will first investigate the definition and classification of “depression” in modern clinical psychology. Moreover, this research will collect and compile the causes of depression found from scholarly sources as reliable references. Secondly, this research will also examine the application and interpretation of the word “depress” from early discourses by tracing back to the Buddha's era such as the Āgama. Furthermore, the prevention and treatment for depression is also a keen topic of discussion nowadays. In terms of treatment, there are drug therapies and psychological counseling; on top of that, the rich studies conducted in modern clinical psychology have resulted in more solutions in this field.Hence, instead of the discussing above, this research will focus on the aspect of “prevention”, which is suggested by the “Four Factors for Stream-entry”─(1) association with good-knowing advisors, (2) hearing the true Dharma, (3) proper consideration, and (4) practicing in accordance with the Dharma─as the prevention of “depression.” Of course, within the vast teachings of the Buddha, I believe that there are many other theories and methods other than the “Four Factors for Stream-entry” that can be applied to the prevention and treatment of“depression.” In order to avoid complex and lengthy narratives, this research will mainly illustrate the aspect of “prevention” instead. I hope this paper will narrow the distance between the Buddhist community and the psychology field, while establishing a platform for more interaction and exchange for both sectors in the future. As for my personal expectations, my goal is to bring forth discoveries and continuous growth in effective preventions and therapies related to depression from Buddhist discourses for the benefit of all mankind and society. Lastly, I wish for my research to implement the spirit of Buddhist compassion.