Depression is a disorder characterized by significant and persistent depressed mood, and in severe cases, suicidal thoughts and behaviors may occur. Most cases have a tendency to have recurrent episodes, and most episodes can be remitted with each episode, and some can have residual symptoms or become chronic. Clinical symptoms: ① Depressed mood, depression, sadness, unhappiness, lack of confidence and hope for the future, even pessimism and despair, low self-esteem, possible self-criminalization, self-blame, delusions and self-injurious suicidal ideas and behaviors. (ii) Delayed thinking, manifested by slow thinking speed, slow reaction and reduced active speech. ③Cognitive impairment, manifested as memory loss, attention deficit, increased alertness, and learning difficulties. ④Decreased volitional activity, slow behavior, passive life, laziness, inability to do things, reluctance to contact and interact with the surrounding people, and in severe cases, depressive xerostomia pleasure deficit, the patient does not feel relaxed and happy inside, and cannot experience pleasure from life. Fatigue and weakness, decreased energy. ⑤ Somatic symptoms Sleep disorder, severe insomnia (difficulty in falling asleep, early awakening, shallow sleep, excessive dreaming), appetite disorder, no appetite, low energy, fatigue and weakness, decreased sexual function, weight loss, multiple somatic discomfort, and symptoms aggravated in the morning. Treatment: I. Medication: SSRIs, such as paroxetine, sertraline, fluoxetine, citalopram, fluvoxamine, etc.; SNRIs, such as venlafaxine, duloxetine, NaSSAs, such as mirtazapine. Of course, these are not the only drugs currently used in clinical practice. They also include the classical tricyclic antidepressants as well as newer antidepressants. Psychotherapy: It is suitable for mild to moderate depression without negative perceptions in the acute stage, as well as the consolidation and maintenance treatment after the control of symptoms in the acute stage of all kinds of depression, which can be carried out simultaneously with drug treatment. Physical therapy includes modified electroconvulsive therapy (MECT) and repetitive transcranial magnetic stimulation (rTMS). ps: at least 10% of patients with depression can have manic episodes, which should be diagnosed as bipolar disorder. According to the World Health Organization, depression has become the 4th most common disorder in the world, and is expected to become the second most common disorder after coronary heart disease by 2020. In the acute phase, the first priority is to take strong measures to relieve the patient’s pain, relieve the symptoms and control the attack as early as possible; after controlling the symptoms to achieve recovery in the acute episode, a long course of treatment should be given, including preventing relapse, preventing recurrence and improving the prognosis. Psychotherapy is very important to help the remission of depression and the prevention of recurrence of depression.