Its primary characteristic is its high incidence. The WHO estimates that there are about 340 million depressed people in the world. The situation of depression in China is also not optimistic, the prevalence of depression in China is about 10%-15%, which is similar to the statistical results of developed countries. The World Health Organization conducted a survey on the lifetime prevalence of depression, and the results showed that about 11% of people have experienced a fairly severe, treatment-needing depression at some point in their lives. This equates to about 1 in 10 people who have suffered or will suffer from depression, and the WHO states that by 2020, depression will be the second most important health problem affecting the world. Second, depression is very dangerous. The impact of monophasic depression and major depressive disorder on the “disability-adjusted life year” alone will be 5.7%, ranking among the top 10 important causes of disability. Depression has become the leading cause of disease burden among women aged 15-44 in both developed and developing countries. Depression not only brings a great burden to society, but also causes a serious family burden and leads to family dysfunction. The adverse effects of depression on families have exceeded those of chronic diseases such as hypertension, coronary heart disease, diabetes, and cancer. Again, it has the characteristic of easy recurrence. Research studies show that 50% of depression patients do not relapse after the first episode is controlled; that means half of the depression patients have recurrent depression episodes for various reasons. In addition, it is characterized by complex symptoms. Its symptom composition is complex and diverse, usually accompanied by a variety of non-specific somatic symptoms, including changes in appetite or body mass, loss of energy, dizziness, chest tightness and pain, which can easily lead to missed or misdiagnosis and ultimately delayed treatment.