Sleep disorders are serious issues in modern society. There has been marked scientific interest in sleep for a century, with the discoveries of the electrical activity of the brain（EEG）, sleep‒wake system, rapid eye movement（REM）sleep, and circadian rhythm system. Additionally, the advent of video‒polysomnography in clinical research has revealed some of the consequences of disrupted sleep and sleep deprivation in psychiatric disorders.
 Decades of clinical research have demonstrated that sleep disorders are intimately tied to not only physical disease（e. g., lifestyle‒related disease）but psychiatric illness. According to The International Classification of Sleep Disorders（2005）, sleep disorders are classified into 8 major categories：1）insomnia, 2）sleep‒related breathing disorders, 3）hypersomnias of central origin, 4）circadian rhythm sleep disorders, 5）parasomnias, 6）sleep‒related movement disorders, 7）isolated symptoms, and 8）other sleep disorders.
 Several sleep disorders, including obstructive sleep apnea syndrome, restless legs syndrome, periodic limb movement disorder, sleepwalking, REM sleep behavior disorder, and narcolepsy, may be comorbid or possibly mimic numerous psychiatric disorders, and can even occur due to psychiatric pharmacotherapy. Moreover, sleep disorders may exacerbate underlying psychiatric disorders when left untreated. Therefore, psychiatrists should pay attention to the intimate relationship between sleep disorders and psychiatric symptoms.
 Sleep psychiatry is an academic field focusing on interrelations between sleep medicine and psychiatry. This mini‒review summarizes recent findings in sleep psychiatry. Future research on the bidirectional relation between sleep disturbance and psychiatric symptoms will shed light on the pathophysiological view of psychiatric disorders and sleep disorders.