Background <p> Patients with severe mental disorders (SMD) face a heavy financial burden, and somatic comorbidity is one of the factors that cannot be ignored. The purpose of this study is to understand the current status of somatic comorbidity in patients and to explore the relationship between medical expenses and different somatic disease comorbidities.</p> Method <p>The group obtained medical data of 4940 patients in 2019 through a follow-up survey. Descriptive statistics were used to analyze the distribution of patient co-morbidities, and CLAD was used to analyze the impact of various factors on patient expenses.</p> Results <p>The most common comorbidity was circulatory disorders (36.6%), followed by respiratory disorders (32.3%), digestive disorders (30.6%) and endocrine, nutritional or metabolic disorders (29.8%). As the types of somatic comorbidity increase, the expenses will also increase. In terms of comorbidity types, a total of 9 ICD-11 chapter group diseases will lead to increased expenses, while 5 chapter group diseases have no statistically significant impact on expenses.</p> Conclusions <p>This study found that comorbidities are widespread in patients with SMD, and most of them lead to a significant increase in patients’ medical expenses. Therefore, the treatment of patients with severe mental disorders should take into account the needs of the prevention, management and treatment of the comorbidity of the population, reduce the occurrence and development of patients’ somatic comorbidity, and thus reduce the burden of patients’ medical expenses.</p>