Dreams are a normal human physiological phenomenon, a subconscious expression of emotions, and they have a different nature due to different stimuli and the nature of stimuli. Some dreams can cause panic and extreme uneasiness, such as being chased, being robbed and making a fool of oneself in public, etc. This is called a nightmare, and long-term nightmares will affect the quality of sleep. Dreams are a special manifestation of the body’s internal mental activity, and so are nightmares. The main causes of nightmares include four parts. External environmental factors: some factors will directly affect the sleep situation, such as room temperature, poor sleep environment, sleep posture error, winter covers too thick, etc. caused by physical discomfort; daytime exposure to too many stimulating things can also cause abnormal excitement in the brain, often nightmares. Psychological factors: It is often said that “there are thoughts and dreams at night”, work pressure, thinking about problems lead to a state of psychological depression, if some people who have experienced major trauma and change always repeat the previous scene, will be easy to have nightmares. Physiological factors: According to the survey, women have more nightmares than men, because women feel more strongly about nightmares, and women are more likely to bring anxiety to sleep; children are more likely to have nightmares than adults, because the brain is not fully developed, and emotions are easily affected by the outside world. Somatic factors: Related studies have confirmed that frequent nightmares can indicate certain diseases, such as long-time dreams about a certain part of the clinical manifestations of the disease, may be the health of the part of the problem, but is not certain, further examination is needed. In general, there are reasons for always having nightmares, and it is important to find the triggers and solve them in time, taking into account your own conditions.