Psychometric properties of the symptom check-list-90-R in prison inmates

The aim of this study was to investigate the reliability, construct and criterion validity of the Symptom Check-List-90-R (SCL-90-R) for prison inmates. A sample of 427 adult prisoners was assessed at admission to the penal justice system in the metropolitan region of Santiago de Chile using the SCL-90-R and the mini international neuropsychiatric interview. We tested internal consistency using Cronbach's alpha. We examined construct validity using Principial Components Analysis and Confirmatory Factor Analysis (PCA and CFA) as well as Mokken Scale Analysis. Receiver Operating Characteristic (ROC) analysis was conducted to examine external criterion validity against diagnoses established using structured clinical interviews. The SCL-90-R showed good internal consistency for all subscales (α=0.76-0.89) and excellent consistency for the global scale (α=0.97). PCA yielded a 1-factor structure, which accounted for 70.7% of the total variance. CFA and MSA confirmed the unidimensional structure. ROC analysis indicated useful accuracy of the SCL-90-R to screen for severe mental disorders. Optimal cut-off on the Global Severity Index between severe mental disorders and not having any severe mental disorder was 1.42. In conclusion, the SCL-90-R is a reliable and valid instrument, which may be useful to screen for severe mental disorders at admission to the prison system.