Patients with undifferentiated somatoform disorder complain of one or more somatic symptoms, for which they are distressed; however, medical examination does not reveal evidence of somatic disease or any organic pathology. The duration of the disease is more than six months and there is significant social dysfunction. Common symptoms include fatigue, lack of appetite, and gastrointestinal or urinary tract discomfort. This clinical type can be seen as an atypical somatization disorder. Its symptoms are less extensive and less abundant than those of somatization disorders, and its duration is not always longer than 2 years. The exact etiology of undifferentiated somatoform disorder is unknown. Studies in recent years suggest that these disorders are associated with the following factors. 1, genetic factors: reports suggest that somatoform disorders are associated with genetic susceptibility qualities. In a study of a group with chronic functional pain, it was demonstrated that its positive family history was significantly higher than that of organic pain; a multifactorial analysis showed a positive correlation between family genetic history and the amount of pain. 2, personality factors: the authors’ study found that both male and female patients had their MMPI contours in types 1, 2, 3, and 7, and their two-point codes were basically consistent with the personality traits of neuroticism. Sterm’s study found that patients with somatoform disorders often combined with certain personality disorders, with passive-dependent, performance-based, and sensitive-aggressive types more common. 3, neurophysiological and neuropsychological factors: research has been found that patients with somatoform disorders have altered brainstem reticular attention and arousal functions, studies on brain function asymmetry link the sensory, attention and emotional alterations of conversion disorders to the way the right hemisphere of the brain processes information, brain research on somatoform disorders points to the second sense, and this area seems particularly suitable to explain its neurophysiological and neuropsychological dynamics mechanisms. It is thought that neuroendocrine, autonomic and blood biochemical alterations in the body during emotional conflict lead to changes in blood vessels, internal organs, and muscle tone, and that these physiological responses are perceived by the patient as somatic symptoms.