At the 10th World Congress on Pain organized by the International Association for the Study of Pain (IASP) the participating experts reached a consensus that chronic pain is a disease. Then the treatment of this disease should be comprehensive and systematic, not just for pain symptoms. We call the category of pain that persists beyond the expected course of recovery chronic pain. Some consider it to last at least more than 30 days, others more than 12 months, but the vast majority of scholars consider pain that lasts more than 3 months to be chronic pain. Its clinical process is not only longer than that of acute pain, but more importantly, its clinical manifestations are more complex and diversified, and the application of general or single treatment methods or medications cannot achieve satisfactory relief or complete control of pain. In this process, because of the prolonged pain, the patients have mental and emotional changes, and at the same time, their life and social abilities are reduced. Ge Xiaodong, Department of Pain, Chaoyang Hospital, Beijing Chronic pain mainly includes: ① prolonged injurious pain, such as lumbar muscle strain. ② Many neuropathic pain, such as trigeminal neuralgia, painful diabetic neuropathy, etc.. ③ Long-term visceral pain, such as endometriosis. Cancer pain. ⑤ Others, such as phantom limb pain. These types of pain have more complex pathological processes and formation mechanisms, involving multiple tissues or organs of the body. So how can a pain physician determine whether a patient with chronic pain is depressed or already in a depressive state? There are several scales for assessing depressive states, such as the Hamilton Depression Inventory, the Beck Depression Inventory, etc., and a more commonly used test is the Self-Depression Scale (SDS). The test consists of 20 questions, each of which is divided into 4 different levels of answers and recorded with different scores: 1. I feel sullen and depressed. 2. I feel the worst in the morning of the day. 3, I burst into tears or feel like crying. 4, I don’t sleep well at night. 5. I eat less than usual. 6. I do not enjoy close contact with the opposite sex as I used to. 7. I find that I am losing weight. 8. I suffer from constipation. My heart beats faster than usual. 10.I feel tired for no reason. 11, My mind comes in often feeling unclear. 12.I find it difficult to do things that I often do. 13.I feel uneasy and calm. 14.I have no hope for the future. 15.I get angry and excited more easily than usual. 16.I find it difficult to make a decision. 17.I feel that I am a useless person and no one needs me. 18.I have no fun living my life. 19.I think that if I die others will have a better life. 20.The things that usually interest me don’t interest me now. A: Rarely; B: Yes, yes; C: Most of the time; D: The vast majority of the time 1 3 4 7 8 9 10 13 15 19 Questions A: 1 point B: 2 points C: 3 points D: 4 points 2 5 6 11 12 14 16 17 18 20 Questions A: 4 points B: 3 points C: 2 points D: 1 point Multiply the sum of the scores of the above 20 questions by 1.25 to get the depression score, with a score of 50 or less being normal; 51 ～A score of 50 or less is considered normal; 51 to 59 is considered mild depression; 60 to 69 is considered moderate depression; and 70 or more is considered severe depression. This method quantifies the degree of depression, but in most cases it is not easy to do in the clinic, so we must grasp some of the characteristics of the symptoms of depression, which are summarized as follows: ① low mood; ② little interest in anything; ③ inactivity; ④ negativity and pessimism, and even the thought of suicide; ⑤ loss of appetite, weight loss; ⑥ sleep disorders mainly manifested as early awakening; ⑦ the above situation has daytime and nighttime, the morning or the morning is at its lowest point, and the afternoon or the evening is at its lowest point. In the morning, it is at its lowest point, and gradually improves in the afternoon or evening. After the appearance of these manifestations above, we have to think that there has been depression or depressive state. For what we often call neurasthenia can also be considered depression. As a result of long-term chronic pain in patients with these conditions. And these symptoms mostly overlap with the physical or mental symptoms of depression, and they are interrelated in 3 main ways: depression itself can cause pain; (2) depression and chronic pain can occur at the same time; and (3) depression can be the result of coping with chronic pain for a long time. To some extent, chronic pain and depression partially share the same “neurobiological pathway”. Short-term pain, or acute pain, stimulates the sympathetic nervous system, causing it to become aroused and increasing the synaptic release of catecholamines and 5-hydroxytryptamines, such as norepinephrine, which is manifested as an increase in heart rate, retraction of the stimulated limb, and vasoconstriction of corresponding tissues, in an attempt to minimize the damage caused by the stimulus, which can be regarded as a protective response of the body. However, in patients with chronic long-term pain, most of the catecholamines and 5-hydroxytryptamines in the synapses of the nerve cells are depleted or insufficient in quantity, resulting in depression with low mood, lack of interest in doing anything, and unwillingness to engage in activities, among other negative manifestations. These are just some of the major factors that are recognized as causing depression, but there are other factors that are not recognized, such as genetic factors. Some people with depression are genetically predisposed and are significantly more likely to be depressed than normal, even if their childhood and adulthood have been smooth sailing. Although genetic correlations have been observed, it is difficult to find the appropriate genes. This is because depression is controlled by multiple genes. Non-genetic factors also play a considerable role, and it has been found that the risk of major depression is significantly increased in patients after acute heart attacks and strokes, and also in cancer patients. In addition to this, a history of childhood abuse also increases the risk of depression, which has been demonstrated in animal experiments with rats and monkeys. The treatment of depression should be carried out by a psychiatric specialist, and in order to achieve a good outcome requires the cooperation of all factors surrounding the patient. Patients can use self-therapy and specialists can use traditional treatments such as electroconvulsive therapy, alternative therapies, experimental therapies, reflexology, hormone supplementation, exercise therapy, and so on. However, more often than not, pharmacotherapy is used. In order to improve the effectiveness of chronic pain treatment, pain doctors must have knowledge or experience in treating depression, because chronic pain also involves many aspects of the patient, in addition to the application of analgesic drugs, but also a combination of a variety of auxiliary drugs, including antidepressants is very important to one of the auxiliary drugs. Antidepressants are one of the most important adjuvant medications, and they are one of the major classes of psychotropic medications. This class of drugs is divided into the first and second generation according to the sequence of application time: 1, the first generation of classic antidepressants: monoamine oxidase inhibitors (MAOI), tricyclic antidepressants (TCA) and tetracyclic antidepressants. Monoamine oxidase inhibitors include isoniazid, phenelzine, isocarbazide, and antiphencyclidine, etc. They inhibit the activity of the monoamine oxidase enzyme and reduce the inactivation of monoamine (dopamine and 5-hydroxytryptamine) transmitters, thus increasing the amount of monopressor transmitters at the synaptic site and exerting antidepressant effects. Tricyclic antidepressants mainly include amitriptyline, nortriptyline, doxorubicin, promethazine, and disopyramide, etc. Their pharmacological effects are to inhibit the reuptake of 5-hydroxytryptamine and norepinephrine, and to enhance the content of 5-hydroxytryptamine and norepinephrine in the center, thus exerting a therapeutic effect on depression. Tetracyclic antidepressants are mainly Maprotiline, Mianserin, etc. The principle of their action is consistent with tricyclic antidepressants. 2.The second generation of new antidepressants: mainly selective monoamine reuptake inhibitors. Selective 5-hydroxytryptamine reuptake inhibitors (SSRI), including paroxetine, fluoxetine, sertraline, citalopram and so on. ② Selective norepinephrine reuptake inhibitors (NRI), such as reboxetine. (iii) Selective reuptake inhibitors (SNRI) of 5-hydroxytryptamine and norepinephrine, including duloxetine, venlafaxine, and milnacipran. ④ Noradrenergic and 5-hydroxytryptamine antidepressants (NaSSA), such as mirtazapine. ⑤ Norepinephrine and dopamine reuptake inhibitors (NDRI), such as bupropion. Most of the above drugs take 1 to 2 weeks to reach a smooth and effective concentration, and some take longer, even up to 4 weeks. Therefore, it is important to explain to the patient in advance that patient compliance is an important aspect of ensuring efficacy. At the same time, we also need to explain to the patient the possible negative effects of the drug, such as blocking the acetylcholine receptor, there may be dry mouth, blurred vision, sinus tachycardia, constipation, urinary retention, glaucoma aggravation, memory dysfunction, etc.; blocking the adrenergic receptors, there may be a strengthening of the antihypertensive effect of perprazolizine, postural hypotension, dizziness, reflex tachycardia; blocking the histamine receptor, there can be a strengthening of central inhibitor effects, such as sedation, drowsiness, weight gain, and decreased blood pressure; blockade of dopamine receptors can occur with extravertebral symptoms, and endocrine changes. If the negative effects are heavy, it is advisable to reduce the dosage, stop the drug or replace it with other drugs. The simultaneous combination of more than two antidepressants is generally not advocated. It should be emphasized here that when antidepressants are used as adjuvants in the treatment of chronic pain, the dose of the drug that can achieve an effective therapeutic effect is much smaller than the dose used in the treatment of depression. Therefore, the negative effects caused by the drug itself are relatively small. In general, for patients with chronic pain in the first signs of depression can be applied antidepressant drugs, according to clinical statistics on the treatment of depression, the earlier the better, and the less likely to relapse, the shorter the treatment time. Be sure to start with a small dose. Most of the antidepressants to achieve stable blood concentration time is more than a week, so be sure to adhere to the continuous application of a week, unless there is a serious negative reaction. The treatment of chronic pain is a complex systematic project involving the patient and all aspects related to him. Antidepressant drugs are only one of the auxiliary analgesic drugs, and it is necessary for us pain doctors to learn, summarize, and accumulate to really use him correctly, well, and timely, and give full play to its auxiliary analgesic effect. So that this chronic disease can be well treated and controlled for the benefit of the majority of patients. References omitted