Depression, also known as depressive disorder, is characterized by significant and persistent depression and is the main type of mood disorder. The depressed mood can range from sullenness to grief, low self-esteem and depression, or even pessimism and anxiety, and may include suicide attempts or behaviors; some cases have significant anxiety and motor agitation; severe cases may have hallucinations, delusions and other psychotic symptoms. Each episode lasts at least 2 weeks, or even several years, and most cases have a tendency to have recurrent episodes. Common symptoms Depressed mood, slowed thinking, reduced volitional activity, impaired cognitive function, and physical symptoms Causes The causes of depression are not clear to date, but it is certain that many biological, psychological and social environmental factors are involved in the pathogenesis of depression. Biological factors mainly involve genetic, neurobiochemical, neuroendocrine, and neuroregenerative aspects; psychological predisposing qualities that are closely related to depression are premorbid personality traits, such as depressive temperament. The exposure to stressful life events in adulthood is an important trigger for the development of clinically significant depressive episodes. However, these factors do not act in isolation, and the interaction between genetic and environmental or stressful factors, and the point at which this interaction occurs, are currently emphasized as having an important influence in the development of depression. Clinical manifestations Depression can manifest itself as a single or repeated multiple depressive episodes, and the following are the main manifestations of depressive episodes Depressed mood The main manifestation is significant and persistent depressed mood, depression and pessimism. In mild cases, depression is characterized by sullenness, unpleasantness and loss of interest, while in severe cases, depression is characterized by pain, pessimism and despair, and life is worse than death. The typical patient’s depressed state of mind has a rhythmical change of heavy in the morning and light at night. On the basis of depressed mood, patients may experience lower self-esteem, feelings of uselessness, hopelessness, helplessness and worthlessness, often accompanied by self-blame and self-guilt, and in severe cases, delusions of guilt and paranoia, and some patients may experience hallucinations. Delayed thinking Patients have slow thinking and association speed, slow reaction, closed thinking, and feel that “the brain is like a rusty machine” and “the brain is like a layer of glue”. Clinically, there is a decrease in active speech, a significant slowdown in speech speed, a low voice, and difficulty in answering questions, and in severe cases, communication cannot be carried out smoothly. The patient has a significant and persistent inhibition of volitional activity. Clinical behavior is slow, passive and lazy, not wanting to do anything, not wanting to interact with people around, often sitting alone, or lying in bed all day, living alone behind closed doors, alienating friends and relatives, avoiding social interaction. In severe cases, the patient may even disregard physiological needs such as eating, drinking and personal hygiene, and may even develop into silent, immobile and inappetent, which is called “depressive rigidity”, but on careful mental examination, the patient still shows painful depression. Patients with anxiety may have symptoms such as fidgeting, finger grasping, hand rubbing or pacing around. Severe cases are often accompanied by negative suicidal ideation or behavior. Negative pessimistic thoughts and self-blame, lack of self-confidence can lead to desperate thoughts, thinking that “ending one’s life is a relief”, “one is redundant in the world”, and can make suicide attempts develop into suicidal behavior. This is the most dangerous symptom of depression and should be monitored. Cognitive impairment Studies have concluded that depressed patients have cognitive impairment. This is mainly manifested by decreased near memory, attention deficit, prolonged reaction time, increased alertness, poor abstract thinking, learning difficulties, poor verbal fluency, reduced spatial perception, eye-hand coordination, and mental flexibility. Cognitive impairment leads to social dysfunction and affects the long-term prognosis of patients. Somatic symptoms The main symptoms are sleep disturbance, fatigue, loss of appetite, weight loss, constipation, pain in any part of the body, loss of libido, impotence, and amenorrhea. Physical complaints of somatic discomfort can involve all organs, such as nausea, vomiting, heartburn, chest tightness, sweating, etc. Symptoms of autonomic dysfunction are also more common. The complaints of pre-morbid somatic disorders are usually aggravated. Sleep disorders mainly manifest as early awakening, usually 2 to 3 hours earlier than usual, and inability to fall back to sleep after waking, which is characteristic for depressive episodes. Some present with difficulty falling asleep and not sleeping deeply; a few patients present with excessive sleep. Weight loss is not necessarily proportional to appetite loss; a few patients may have increased appetite and weight gain. Examination For patients suspected of depression, in addition to a comprehensive physical examination and neurological examination, attention should be paid to ancillary examinations and laboratory tests. To date, there are no specific tests for depressive disorders. Therefore, current laboratory tests are mainly designed to exclude depression due to substance and somatic disorders. There are 2 laboratory tests of some significance, including the dexamethasone suppression test (DST) and the thyrotropin-releasing hormone suppression test (TRHST). Diagnosis The diagnosis of depression should be based mainly on medical history, clinical symptoms, duration of illness and physical examination and laboratory tests, and the diagnosis of typical cases is generally not difficult. At present, the common international diagnostic criteria are ICD-10 and DSM-IV. ICD-10 is mainly used in China, which refers to first-episode depression and recurrent depression, excluding bipolar depression. Patients usually have typical symptoms such as depressed mood, loss of interest and pleasantness, low energy or fatigue. Other common symptoms are (1) decreased ability to focus and pay attention; (2) decreased self-evaluation; (3) self-guilt and feelings of worthlessness (even in mild episodes); (4) perception of a bleak and pessimistic future; (5) self-injurious or suicidal thoughts or behaviors; (6) sleep disturbances; and (7) decreased appetite. The duration of the illness is at least 2 weeks. Treatment The treatment of depressive episodes should achieve three goals: (1) to improve the clinical cure rate and minimize the disability and suicide rates, the key is to completely eliminate clinical symptoms; (2) to improve the quality of life and restore social functions; (3) to prevent relapse. Treatment principles: (1) individualized treatment; (2) gradual increase in dose, as far as possible, the smallest effective amount, so as to minimize adverse reactions, in order to improve compliance; (3) full amount and full course of treatment; (4) as far as possible, a single drug, such as poor efficacy can be considered to switch treatment, augmentation therapy or combination therapy, but need to pay attention to drug interactions; (5) informed notification before treatment; (6) close observation of changes in the condition and adverse reactions during treatment and (6) Close observation of changes and adverse effects during treatment and timely management; (7) Combined psychotherapy to increase the efficacy; (8) Active treatment of other physical diseases, substance dependence, anxiety disorders, etc. that are co-morbid with depression. Medication is the main treatment for moderate depressive episodes or above. Currently, the first-line antidepressants include selective 5-hydroxytryptamine reuptake inhibitors (SSRI, representing fluoxetine, paroxetine, sertraline, fluvoxamine, citalopram and escitalopram), 5-hydroxytryptamine and norepinephrine reuptake inhibitors (SNRI, representing venlafaxine and duloxetine), norepinephrine and specific 5-hydroxytryptaminergic antidepressants (NaSSA, representing the drug mirtazapine), etc. Traditional tricyclic and tetracyclic antidepressants and monoamine oxidase inhibitors have been significantly reduced in use due to their high adverse effects. Psychotherapy For patients with depressive episodes with significant psychosocial factors, psychotherapy is often combined with pharmacotherapy. Commonly used psychotherapies include supportive psychotherapy, cognitive-behavioral therapy, interpersonal therapy, marital and family therapy, and psychodynamic therapy, among which the efficacy of cognitive-behavioral therapy for depressive episodes has been recognized. Physical therapy Patients with severe negative suicidal attempts and those who have failed to be treated with antidepressants can be treated with modified electroconvulsive therapy (MECT). Maintenance treatment with medication is still required after electroconvulsive therapy. A new physical therapy, repetitive transcranial magnetic stimulation (rTMS) therapy, has emerged in recent years and is mainly indicated for mild to moderate depressive episodes. Prevention A study of depressed patients followed for 10 years found that 75% to 80% of patients had multiple relapses, so depressed patients need preventive treatment. More than 3 episodes should be treated for a long time, even with lifelong medication. Most scholars believe that the dose of maintenance medication should be the same as the treatment dose, and regular outpatient follow-up observations should also be made. Psychotherapy and social support system also play a very important role in preventing relapse of the disease. Patients should be relieved or relieved of excessive psychological burden and pressure as much as possible, to help them solve practical difficulties and problems in life and work, to improve their coping ability, and to actively create a good environment for them to prevent relapse.