When I have been treating patients with anxiety or depression in recent years, I pay a lot of attention to their dreams. One of the things I cared about most was the nightmare dreams of my patients, both for understanding the condition and for judging the effectiveness of the treatment. I have found that there are two kinds of “nightmares”. One is a dream with a lot of scary and dangerous scenarios, situations or experiences, such as dreams of being chased, beaten, threatened, or in a dangerous and isolated situation such as struggling in deep water, on the edge of a cliff or mountain, attacked by a fierce animal, or in a huge disaster such as an earthquake, car accident or air crash. Other people are in a dilemma when they face a major test in the real world in a nightmare dream, such as when they are about to take a college entrance exam but cannot find their pass or forget where the exam room is, or forget to bring the stationery for the exam. Many people will wake up in this fearful dream state and experience significant anxiety, with palpitations, cold sweats and other vegetative symptoms. Patients who have these dreams frequently during sleep often have significant outward expressions of anxiety, as well as a clear experience of internal anxiety, and are often accompanied by typical physical symptoms of anxiety such as palpitations, chest tightness, shortness of breath, dry mouth, bloating, frequent urination, and excessive sweating. Patients with more severe anxiety symptoms may have such dreams even during a short lunch break or snooze. Many people who have such dreams meet the diagnostic criteria for anxiety disorders. Or conversely, most patients who meet the diagnostic criteria for anxiety disorders have these types of nightmares. Another type of nightmare dream is one that causes unpleasant experiences such as pain, sadness, hopelessness, helplessness, or hurt feelings. For example, dreams of being bullied, ridiculed, or embarrassed but unable to escape or resist, or dreams of being killed and not being rescued, or dreams of the strange death of a loved one, or dreams of trudging through an endless quagmire, being trapped in a vast wilderness with no way out, being trapped in an empty and dark room with no way out, or dreams of needing to shop but having no money, or dreams of losing a beloved or precious object that cannot be retrieved, or dreams of being seriously ill but having no way to seek medical help. or dream of being seriously ill and having nowhere to turn to for medical help. Many people also have dreams of childhood sadness and humiliation, such as being publicly criticized and humiliated by the elementary school teacher or being verbally abused by a group of classmates. These people also have clear manifestations and inner experiences of depressed mood, sullenness, easy sadness or boredom during the daytime, and most of them have clinical manifestations that fully meet the diagnostic criteria for depression. In addition, there are some other characteristics of the above mentioned nightmares. For example, there are many people who frequently have both of the above nightmare dreams during the same period of time, and these people often have both anxiety and depressive symptoms, and even meet the diagnostic criteria for both mental disorders at the same time. In many cases, having both of these nightmares also reflects a previous traumatic experience, and these dreams are often repeated in the form of “déjà vu”. People who have these nightmare dreams may have “sleep talking” or screaming or crying at the same time. If the dreaming is clear enough, the verbal statements are often reflective of panic and pain, and are accompanied by a corresponding voice and tone. In my clinical practice, I have found that nightmares with significant emotional “disturbances” can serve as both a marker of the nature of the illness and as a barometer of changes in the illness and an indicator of the efficacy of treatment. Whether the nightmares are reflective of anxiety or depression, the frequency of nightmares, the intensity and persistence of the emotions reflected in the dreams can indicate whether the patient’s condition is worsening or decreasing. For patients with systematically treated anxiety or depression, as their condition improves and their anxiety and depressive symptoms decrease, the frequency of nightmares gradually decreases, their duration gradually shortens, and the intensity of the negative emotions accompanying the nightmares gradually diminishes. However, after most patients have reached clinical recovery, their nightmares often do not disappear and will continue to occur intermittently or occasionally for a longer period of time. At this point, I basically continue to use the main medication used to treat anxiety and depression until the patient is able to confirm that they have not had such nightmares for more than three months before they are considered to be in true and complete remission, and only then do they begin the medication reduction phase. I have found that in most cases, the complete disappearance of these nightmares lags far behind the disappearance of clinical symptoms. In my experience, it is worthwhile for doctors and patients to try to focus on the changes in nightmares to help determine the nature, severity and response to treatment of the disease. Of course, I also hope that scholars doing sleep research will explore the deeper principles of these phenomena and perhaps discover indicators that can be used for diagnosis as well as methods that can be used for treatment.