At present, research on improving the efficacy of ECT is carried out mainly by psychiatrists in terms of aspects such as electroshock mode, electric quantity and stimulation site18, while anesthesiologists are concerned mainly with the different anesthetic compounds or administration modes19, 20. By analyzing the clinical characteristics of nonremission patients, this study intended to improve the evaluation and regulation of patients before anesthesia to further improve the efficacy of ECT. We found that atherosclerosis, diabetes, COPD and smoking may be high-risk factors for nonremission ECT. To date, there is no relevant research, but it is certain that these factors will affect the symptoms of depression.
There is an interactive relationship between depression and atherosclerosis. Studies have shown that depression increases the risk of atherosclerosis. First, from the perspective of pathophysiology, depression is accompanied by immune dysregulation21, and in this context, the levels of a variety of peripheral inflammatory biomarkers are increased22. On the other hand, there are alterations in the nitric oxide (NO) system23. Endothelium-derived NO, through its vasodilator properties, participates in the modulation of vascular tone24. These factors promote atherosclerosis. In addition, the behavioral effects of depressive symptoms are considered to be another source of subclinical atherosclerosis, such as sleep disorders, sedentary behavior and obesity, smoking and alcohol consumption. Sleep disorders lead to impaired vascular endothelial function25, sedentary behavior causes intimal thickening of arteries26, and smoking and obesity lead to the formation of atherosclerotic plaques27, all of which contribute to an increased atherosclerotic burden. Depression and atherosclerosis have a common pathophysiological basis28, 29, and it has been confirmed that intracranial atherosclerosis will aggravate the symptoms of depression30. It has been reported that depression patients with atherosclerosis have a poor response to drug treatment31. However, ECT treatment has not been reported. Our study found that atherosclerosis is the most important reason for nonremission after ECT, showed that atherosclerosis may have an impact on depression in another way, and indicated that it will influence the treatment efficacy. Some studies have shown that the treatment of atherosclerosis can reduce depression32. Therefore, we should treat atherosclerosis when evaluating such patients, as this may improve the efficacy of ECT.
Evidence has also suggested a bidirectional relationship between diabetes and depression33, 34. Numerous studies have confirmed that the course of depression in patients with diabetes is more severe and that depression episode relapses are more frequent. From a pathophysiological perspective, depression is highly consistent with diabetic complications. These complications include macrovascular complications (such as coronary artery disease), microvascular complications (diabetic retinopathy, neuropathy, nephropathy or end-stage renal disease) and bidirectional complications (depression may increase the risk of diabetic complications). On the other hand, these complications also affect the occurrence and development of depression17, 35. Our research also shows that diabetes is a high-risk factor affecting the efficacy of ECT, which may be related to the aggravation of depressive symptoms by diabetic complications. The treatment of diabetes can reduce the symptoms of depression36, which may help to improve the efficacy of ECT. However, there is still a lack of prospective studies to support this conclusion.
Our study also found that COPD and smoking are key indicators affecting the efficacy of ECT. These two factors are different from the previous two high-risk factors. Although they do not directly cause vascular disease, they affect the development of depression in other ways. COPD causes hypoxia by destroying the lung capillary bed and causing poor airway ventilation, leading to a decrease in neurotransmitter serotonin activity and eventually depression37, 38. Hypoxia may also cause global suppression of cerebral metabolism (energy production), leading to depression39, 40. A series of symptoms of COPD are also causes of depression, and dyspnea, as the core symptom of COPD, may play an important role in the causal relationship between COPD and depression41, 42. These patients are less active, have a lower quality of life and have a worse mood. Smoking has an impact on vascular disease and lung disease, aggravating these diseases43, 44. Smoking may also be an independent risk factor for depression45, 46. This may be the reason why smoking affects the efficacy of ECT.
Treatment with these risk factors can improve the depressive symptoms of patients, but the correlation between these factors and ECT has not been reported. In addition, psychiatrists can improve the efficacy of ECT by changing the stimulation power, using different stimulation sites, and changing the stimulation mode, among other actions18, 47, 48. Therefore, we hope that when anesthesiologists evaluate patients, they will pay attention to and address these risk factors to further improve the efficacy of ECT.