Depression is a dysfunctional state of the brain, a common disorder of the mind, characterized by depressed mood, diminished interest, reduced enjoyment of life, and slowed thinking and association. Depression is the most common type of mental disorder, with a high incidence, known as the “cold” of the mind, everyone has a depressed mood, not timely regulation will suffer from depression, bringing serious mental, emotional and physical suffering, to the family, work and society will bring damage. Depression is mainly characterized by low mood, reduced interest, pessimism, slow thinking, lack of initiative, self-blame, poor diet and sleep, fear of suffering from various diseases, feeling unwell in many parts of the body, a common mental illness, and in severe cases, suicidal thoughts and behaviors. This disorder, depression, may range from mildly poor mood to severe depression, and it is distinct from normal low mood. The core symptom of depression is a lack of pleasure. Pleasure deprivation means “loss of the ability to experience pleasure”. In other words, after suffering from depression, you can’t find happiness, even things that used to make you feel happy and joyful don’t make you feel happy anymore, things that seem interesting to others don’t seem interesting to you, and whatever you do doesn’t feel interesting. We all know that happiness is a feeling, an experience, individuals have different feelings about happiness, and individuals have their own definition of happiness. But no matter what kind of happiness, you need to feel and experience it, and if you lose this ability, then you can’t feel and experience the feeling of happiness from life. The core symptoms of depression are low mood; often accompanied by feelings of uselessness, helplessness, and hopelessness, reduced activity, alienation from others, slow behavioral movements, and a passive life; some people also experience insomnia, decreased appetite, weight loss, decreased sexual desire, and even suicidal thoughts and behaviors. Most depression exhibits recurrent episodes and some will become chronic. To reduce the risk of recurrence and chronicity it is best to treat early, systematically and thoroughly. What is depression? Human emotions are innate, usually positive and negative, such as happiness, excitement, satisfaction, love, pride, positivity, etc. These emotions are positive, while those of sadness, sorrow, fear, depression, anger, disgust, regret, shame, negativity, etc. are negative emotions. Whether it is positive or negative emotions, they are all normal emotions. Depression is a normal low, depressed mood, which is what we usually call a low mood or a bad mood. Although depression is a negative emotion, depression belongs to a normal emotion. Life is sour and sweet, life is bitter and happy, sad and happy, success and failure, good and bad, so people produce joy, anger, worry, thought, sadness, fear, fear and other mood swings are perfectly normal and natural. Depression is also a normal emotional response that combines negative emotions such as sadness and grief. In life, general depression is a very common emotional component and is a common human condition. When people encounter mental stress, life setbacks, painful situations or birth, old age, illness or death, it is natural to have emotional changes, especially depressive mood. Depression is also a mental illness with emotional depression as the main manifestation, and is a pathological depressive disorder. The determination of depression includes symptom criteria, severity criteria and disease duration criteria.