Prevalence and Related Factors of Subthreshold Depression among Chinese Residents: A National Cross-sectional Study

Background Subthreshold depression (SD) impairs quality of life and escalates the risks of progression to major depression. However, it is frequently overlooked in primary healthcare settings. Objective This study investigates the prevalence of SD and its associated factors among Chinese residents. Methods In this cross-sectional study, we recruited 9,546 residents over the age of 18 from 120 cities across China. Data from sociodemographic questionnaires and validated scales (SD, self-efficacy, social support, family health, self-rated quality of life, and health literacy) were analyzed using Chi-square, Mann–Whitney U tests, and logistic regression. Model performance was assessed through receiver operating characteristic curves. Results The prevalence of SD was 34.4%. SD was less likely to occur among residents who were male and older and had better perceived social support, greater family health, better self-rated quality of life, and higher levels of health literacy. In contrast, individuals with debt, siblings, or chronic diseases, and those who were unmarried, divorced, or widowed were at higher risk. The model showed moderate predictive accuracy (area under the curve = 0.68, 95% confidence interval: 0.67–0.70). Conclusion The study highlights a high prevalence of SD (34.4%) among Chinese residents, influenced by sociodemographic and psychosocial factors. Protective factors included male gender, older age, stronger social support, better family health, greater self-rated quality of life, and higher levels of health literacy. Conversely, having debts, being unmarried/divorced/ widowed, having chronic diseases, and having siblings increased the risk. Targeted prevention strategies should address modifiable factors, such as social support and health literacy. The moderate predictive efficacy of the model suggests potential for early screening but warrants further exploration of additional predictors.