Insomnia is one of the most common sleep disorders and is mainly characterized by unsatisfactory quality and/or quantity of sleep. Almost everyone has experienced insomnia, which can be characterized by difficulty falling asleep, early awakening, difficulty maintaining sleep, waking up easily and having difficulty falling asleep again, and sometimes staying awake overnight. Strictly speaking, insomnia is only a symptom of sleep abnormality, it may be a signal of abnormalities in human physiological functions and biological rhythms. The reasons behind the same insomnia can be very different. Classifying insomnia according to its causes, insomnia can be simply divided into primary and secondary insomnia. Somatic diseases, psycho-psychiatric disorders, psychoactive substance use, psychophysiological stress, and environmental changes can cause sleep disorders and insomnia. In these cases, insomnia is secondary to other internal or external factors or just one of the symptoms of other diseases, collectively referred to as secondary insomnia. Some major physical diseases such as organic brain diseases (e.g. Alzheimer’s disease, brain tumor, traumatic brain injury, encephalitis, cerebrovascular disease, etc.), endocrine diseases (e.g. hyperthyroidism, diabetes, etc.), chronic cardiopulmonary diseases (e.g. coronary heart disease, hypertension, emphysema, etc.), cancer and vital organ failure often cause insomnia due to abnormal physiological functions of the body and disruption of endostasis. In addition, some chronic physical diseases such as gastroduodenal ulcer, prostate hypertrophy, gout, rheumatoid arthritis, etc. can also cause insomnia because they cause a decrease in body comfort at night and bring disturbance to normal sleep. The use of psychoactive substances such as alcohol, tobacco, heroin, stimulants, hallucinogens and other psychoactive substances can affect human emotions, behavior and other mental activities, and are often accompanied by insomnia during use, after addiction or withdrawal. Insomnia is also one of the concomitant symptoms of some common psychiatric disorders such as anxiety, depression, obsessive-compulsive disorder, neurasthenia, somatization disorder, schizophrenia, mania and other disorders. And suffering from strong mental stimuli such as the death of a loved one, divorce, unemployment, rape, etc. may cause acute or chronic stress disorder, with some transient or persistent mental and physical symptoms including insomnia, of which insomnia is one of the most common symptoms of chronic stress disorder. Some strong physiological stimuli such as cold, heat, noise and short-term or frequent changes in sleep environment such as business trips, jet lag, night shifts, etc. are also common causes of insomnia. In addition to the above-mentioned secondary insomnia, we often encounter a category of insomnia without any special reason, called primary insomnia. This type of insomnia is common in some patients with chronic, long-term insomnia and is related to genetics and factors such as the patient’s long-established personality, cognitive style, lifestyle habits and sleep hygiene. In addition, there is a special kind of insomnia, which is manifested by the fact that although the patient complains of insomnia, there is no objective evidence of sleep disorder and various sleep-related examinations are not significantly abnormal, and this condition is called subjective insomnia or pseudo-insomnia and poor sleep state perception. In short, the reasons behind the seemingly simple insomnia are various and vary widely. Therefore, once we suffer from insomnia, we must treat it calmly, and we should not leave it alone, or blindly self-medicate, but should go to a professional institution that treats insomnia in time to find the cause, make a clear diagnosis, and treat it comprehensively, so as not to delay the disease or lead to chronic and persistent insomnia.