Staying up late will be detrimental to human health, because the adrenal cortex hormone and growth hormone are all secreted during the night when people are sleeping. The former is secreted before dawn, which can promote the metabolism of carbohydrate in human body, and protect the development of muscle; while the latter is produced only after sleep, which can not only promote the growth and development of young people, but also can delay the aging process of the elderly. As a result, staying up late will cause a variety of harms to human body.First, frequent fatigue and decreased immunityThe most serious sequence caused by staying up late is fatigue and lack of energy. What's more, the immunity of human body will decrease accordingly. And some other symptoms such as cold, gastrointestinal infections, allergies will also appear.Second, headacheThe next day after staying up late, you will suffer from headache when you are at work or at class. You will be unable to concentrate. What's more, long-term staying up late and insomnia will also bring invisible damage to our memory.Third, dark circles and puffinessNight is the time for human body to have a good rest. Without adequate rest, you will feel extremely tired, which will lead to poor blood circulation around the eyes, causing dark circles or blood streak in the white of the eye.Fourth, dry skin, dark spots and acneThe period between 11:00 pm to 3:00 am in the next day is the beauty time, and it is also the time for the meridians in human body to move to gall bladder and liver. If these two organs do not have adequate rest, it will be reflected on the skin. So some problems such as roughness, yellowish face, dark spots and acne will appear. What's worse, long-term staying up late will slowly cause some neurological and psychiatric symptoms such as insomnia, forgetfulness, irritability, anxiety and so on.Fifth, affecting fertilityFor the men and women of childbearing age, if they always stay up late, it will not only affect the motility and quantity of male sperm, but also will affect the secretion of female hormone and the quality of ovum, and it is also likely to influence the menstrual cycle.Sixth, increasing the probability of getting some chronic diseasesPeople who staying up all night always have higher secretion of adrenaline than the average person, which will increase the pressure on metabolism, and thus leading to some chronic diseases, such as hypertension and diabetes.What's more, there are also other harms caused by staying up late, such as poor eyesight or dysfunction of the liver. We should pay special attention to these bad effects, and try not to stay up late at night.---------------------------------Do you always work or study until midnight?Do you often hang out or spend much time in pubs at late night?If you answered yes to either of these questions, you are unfortunately one of the large groups of people who always stay up late. Because of the fierce competition in the society, it seems that everyone has endless work to do and twenty-four hours per day is not enough. Therefore, an increasing number of people stay up late in order to finish the mountainous work. Besides, lots of young people enjoy entertaining at late night. However, many of them are still not aware of the bad effects of staying up late. In fact, it does severe harm to us in three aspects, namely physical health, work efficiency and mental stress.In the first place, staying up late badly impacts on our physical health condition. The human adrenal cortex hormone and growth hormone, which are vital substances for human body, only secrete at night. The former secretes before the dawn facilitating the carbohydrate metabolism and protecting the development of muscle function. The latter only secretes after sleeping. It can improve the growth of the young and slow down the aging of the elderly. However, if people often stay up late, the secretion of these two substances will be gravely impacted. Finally, our health condition will be degraded. It can cause a variety of harms to human body. Normally, frequent staying up late will lead to fatigue and degraded immunity. People may easily get sick when the weather gets a little bit colder or hotter. In addition, it can also cause headache. People may feel heavy in the brain and dizzy for a whole day. Besides, the fertility of both male and female will be impacted. For women, it will affect the secretion of female hormones and the quality of ova. It also tends to affect the menstrual cycle. For men, both the quality and quantity of sperm will be impacted. What is more, staying up late can also damage people’s eyesight, skin and memory capacity, and cause black eyes as well.Furthermore, it negatively impacts on the work efficiency. On the one hand, owing to the discomfort of your health as mentioned above, you may feel distracted from the work. On the other hand, because of the decrease of the memory capacity, your work efficiency will be lower, which means that you may not complete the things as you want. Assume that you are a university student and you plan to review for your psychology examination next week after tomorrow’s class. Nevertheless, you stayed up late yesterday for some reason. Therefore, you probably be late for tomorrow’s class or even skip it. Thus, you must find other time to compensate for it. Afterwards, when preparing your examination, you may feel headache and cannot concentrate on it, thus having difficulty memorizing and understanding the psychological terms and principles. Therefore, your schedule for reviewing chapter 2 and chapter3 will be changed. You can only review chapter 2 and may not finish chapter 3. However, in order to finish reviewing on time, you are more than likely to stay up late again. Then, you will be in the vicious cycle and your work efficiency will be lower and lower.What is also noticeable is that staying up late can bring about mental stress. Since your work efficiency is lower, you probably doubt yourself whether you are a capable person or not. You may think you are not so smart as others and even fear yourself that you can hardly get a good grade in your psychology examination, which makes you feel more anxious and upset. Besides, if you frequently stay up late, you definitely look tired and in low spirits. Therefore, when working on a group project, maybe nobody wants to be in the same group with you, a low-efficient and anxious person. Thus, you will feel separated from others, which possibly makes you more stressed and upset.In conclusion, although we have a lot of work to do and various activities to participate in, staying up late is by no means a good choice for us. It badly impacts on our physical health, lowers our work efficiency and makes us stressed and anxious. Faced with too much work, we should make good arrangements in advance and maintain a healthy lifestyle.