Prevalence and risk factors for depression in somatic symptom disorder patients: a cross-sectional clinical study in China

The comorbidity of somatic symptom disorder (SSD) and depressive symptoms is common; however, the demographic and clinical factors correlated with depression among SSD patients remain unclear. The purpose of this study was to explore the prevalence and associated factors of depressive symptoms in Chinese Han patients with SSD. In this cross-sectional study, 899 outpatients diagnosed with SSD were included. Demographic data were collected, and clinical assessments were conducted, which included blood pressure measurements and laboratory tests for thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), anti-thyroglobulin (TGAb), free triiodothyronine (FT3), free thyroxine (FT4), fasting blood glucose (FBG), and lipid profiles. The participants were evaluated using the Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), Insomnia Severity Index (ISI), and Perceived Social Support Scale (PSSS). Data were analyzed using descriptive statistics, chi-square tests, nonparametric tests, logistic regression analysis, and receiver operating characteristic (ROC) curve analysis with calculation of the area under the curve (AUC), as appropriate. The prevalence of depression in SSD patients was 83.6%. Compared with those without depression, depression in SSD patients was associated with age, age of onset, duration of illness, marital status, TSH, FBG, total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein (LDL-C), systolic blood pressure, diastolic blood pressure, anxiety symptoms, insomnia and levels of perceived social support (all p < 0.05). Multivariate logistic regression analysis indicated that age, TC, insomnia and levels of perceived social support were correlated with depression in SSD patients (all p < 0.01). Among these factors, insomnia had the highest AUC value of 0.908. However, the combination of insomnia and perceived social support achieved an even higher AUC value of 0.926. Our findings suggest a high prevalence of depression in SSD patients. Several factors are associated with depression in SSD patients. Insomnia is a robust risk factor for depression in patients with SSD, and its discriminatory capacity is enhanced when combined with the assessment of perceived social support levels.