Insomnia usually refers to a subjective experience of unsatisfactory sleep duration and/or quality that affects daytime social functioning. Insomnia is characterized by difficulty sleeping (sleep onset longer than 30 min), sleep maintenance disorders (≥2 awakenings throughout the night), early awakenings, decreased sleep quality and reduced total sleep time (usually less than 6 h), accompanied by daytime dysfunction. Insomnia is classified according to its duration: acute insomnia (duration <1 month); subacute insomnia (duration ≥1 month, <6 months) and chronic insomnia (duration ≥6 months). Insomnia can be divided into two categories according to the etiology: primary and secondary. Primary insomnia usually lacks a clear etiology or remains after the exclusion of possible causes of insomnia, and mainly includes three types of psychophysiological insomnia, idiopathic insomnia and subjective insomnia. The diagnosis of primary insomnia lacks specific indicators and is mainly an exclusionary diagnosis. When the possible causes of insomnia have been eliminated or cured, primary insomnia can be considered when the symptoms of insomnia are still left. Secondary insomnia includes insomnia caused by physical diseases, mental disorders, substance abuse, and insomnia related to sleep breathing disorders and sleep movement disorders. Insomnia often occurs together with other diseases, and it is sometimes difficult to determine the causal relationship between these diseases and insomnia, so the concept of comorbid insomnia has been proposed in recent years to describe insomnia that is accompanied by other diseases. The diagnosis of insomnia must meet the following criteria: 1. The presence of one of the following symptoms: difficulty falling asleep, sleep maintenance disorder, early awakening, decreased sleep quality, or non-restorative sleep after waking up in the morning. 2. The above symptoms occur despite the availability of sleep and a sleep-friendly environment. 3. The patient complains of at least one of the following sleep-related impairments in daytime functioning: (1) fatigue or general malaise; (2) decreased attention, attention maintenance, or memory; (3) decreased ability to learn, work, and/or socialize; (4) mood swings or irritability; (5) daytime sleepiness; (6) decreased interest, energy; (7) increased tendency to make mistakes at work or while driving; (8) nervousness, headache, dizziness, or other symptoms related to sleep. headaches, dizziness, or other somatic symptoms associated with sleep deprivation; (9) excessive concern about sleep.