Psychometric properties of the Chinese version of the SF-36v2 in patients with severe mental illnesses in China: factor structure, reliability, and validity

Objective Patients with severe mental illnesses(SMIs) often experience a diminished quality of life(QOL), and a validated tool to assess their QOL remains lacking. This study aimed to evaluate the psychometric characteristics of SF-36v2 among Chinese SMIs patients to determine its suitability for assessing their QOL. Methods We conducted a cross-sectional study involving 924 randomly selected SMIs patients from 23 community health centers in Nanjing, China. The reliability of the SF-36v2 was assessed by Cronbach's alpha and split-half reliability. Factor structure was examined by exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Convergent validity was evaluated using average variance extracted (AVE) and composite reliability (CR). Results The SF-36v2 scale demonstrated good internal consistency, with a Cronbach's alpha of 0.941 and split-half reliability of 0.965. A slight ceiling effect was observed in the Social Function dimension (17.6%). CFA confirmed the acceptability of the hypothesized model, with the measurement model meeting all relevant fit metrics (X2/ df = 1.552, p < 0.05, RMR = 0.037, GFI = 0.950, AGFI = 0.942, CFI = 0.984, NFI = 0.955, RMSEA = 0.024). For each dimension, AVE > 0.5 and CR > 0.7, indicating good convergent validity of the scale. The square root of the AVE from the variables was greater than the correlation between the dimensions in the model, supporting the scale's discriminant validity. Additionally, the PCS (43.74 +/- 10.28) and MCS (43.74 +/- 10.28) scores of patients with SMIs were significantly lower than the Chinese general population norm (p < 0.001). Conclusions The SF-36v2 demonstrated robust psychometric properties, making it a reliable and valid tool for assessing QOL in SMIs patients. Its application can facilitate an objective evaluation of QOL in this population and inform treatment decisions accordingly.