Depression is a state of mind that is characterized by a significant depressed mood and a loss of interest or pleasure in activities that are normally enjoyable. The most common symptoms include: markedly low mood, loss of interest or pleasure, decreased self-confidence or low self-esteem, feelings of worthlessness and guilt, feelings of a bleak future, self-injurious or suicidal thoughts or behaviors, sleep disturbances, eating disorders, decreased libido, decreased energy, easy fatigue, decreased activity, and difficulty or decreased concentration. Such patients are often found in departments other than psychology, such as cardiovascular medicine, gastroenterology, neurology, and oncology, and the rate of depression is especially high in patients with chronic physical diseases, such as acute heart attack 25%, diabetes 27%, stroke 23%, coronary heart disease 27%, cancer 42%, and Parkinson’s disease 61%. Many patients often neglect their mental health, emphasize only their physical symptoms, or are reluctant to admit or conceal their depression, making it difficult for non-psychiatrists to detect it, and patients’ families do not pay enough attention to it, thinking that it is more normal for patients to show depression caused by physical illnesses, and that it is most important to treat physical illnesses. However, from a psychological point of view, depression is potentially very harmful, bringing negative effects on one’s physical condition, life, work and social life in mild cases, and suicide in severe cases, ranking among the top three diseases that cause the highest percentage of deaths. Depression in general hospitals is often insidious, perhaps mild but persistent, and causes a lot of suffering to both the person and the family. It is a disorder that needs to be treated and is treatable; the key is early detection.