Depression is a common mood disorder that can be caused by a variety of reasons, with significant and persistent depression as the main clinical feature, and the depression is not proportional to its situation, and in severe cases, suicidal thoughts and behaviors can occur. Most cases have a tendency to have recurrent episodes, with most episodes resolving, and some may have residual symptoms or become chronic. Depression can occur in at least 10% of patients with manic episodes, at which point the diagnosis of bipolar disorder should be made. Also what we often call depression actually refers to clinical major depressive disorder, which affects 16% of the population at some point in their lives. In addition to the severe emotional and social costs of suffering from depression, the economic costs are also enormous. According to the World Health Organization, depression has become the world’s 4th leading disorder and is expected to become the second leading disease after coronary heart disease by 2020. The etiology and pathogenesis of depression are still unclear, and there are no obvious signs and laboratory abnormalities, but in general it is the result of the interaction of biological, psychological and social (cultural) factors. There are many hypotheses, but the more commonly accepted etiological hypotheses include genetic, biochemical, and psycho-social factors. Depression can be classified as either mild depression or major depression; or depression without psychotic symptoms and depression with psychotic symptoms. Typical clinical symptoms of depression include a decrease in three dimensions of activity: depressed mood, slowed thinking, and reduced volitional activity, while some patients may exhibit predominantly somatic symptoms. If symptoms such as itching of the skin, facial edema, facial flushing occur while taking the drug Zoloft for depression, it may be due to allergy to the drug.