The causes of OCD are not very clear, and there are various hypotheses about its pathogenesis based on psychological and physiological perspectives. 1. Psychoanalytic theory Obsessive-compulsive thoughts and behaviors reflect the subconscious desires of people in their early developmental stages, showing the instinctive, erotic and natural side of human beings. 2. Behavioral perspective Obsessive-compulsive disorder arises because of excessive repetition of stimulus-response and dysregulation of excitation and inhibition in the brain, which leads to the formation of abnormal habits and the establishment of pathological reflexes that cause impulses, thinking and action to stick to a fixed pattern. In particular, adolescents, who are in the developmental stage, may experience obsessive-compulsive symptoms if they do not adapt in social interactions. Work tensions, family discord, and marital problems, as well as accidents, deaths in the family, and major blows, may also cause anxiety, tension, and fear, thus triggering OCD. 3, personality characteristics about 1/3 to 2/3 of the patients before the diagnosis that there is an obsessive-compulsive personality, obsessive-compulsive personality characteristics include timid, cautious, indecisive, serious and old-fashioned to do things in order, strive for meticulous, attention to detail, love of cleanliness. In addition, some twin surveys have found that the incidence of OCD in twin siblings of OCD patients is higher than that of the general population, which also suggests that the occurrence of OCD is related to genetics. 5, neurobiochemical factors The occurrence of OCD may be due to the dysregulation of neurotransmitters in the brain (such as dopamine, 5-HT, etc.), such as 5-hydroxytryptamine (5-HT), which disrupts the information exchange pathways in the frontal lobe and subcortical areas of the brain, leading to the development of OCD. 6, neural structure damage and other organic factors Clinical patients with certain encephalitis, temporal lobe contusion, epilepsy can occur obsessive-compulsive symptoms, surgical treatment showed that the removal of certain parts of the brain (such as the caudal nerve bundle limbic white matter) is effective in improving obsessive-compulsive symptoms suggest that the occurrence of OCD may be related to the function of these parts.