Brief 24-item staged assessment of suicidal and non-suicidal self-injury severity in Chinese college students with positive history: Development and initial validation of the STBI24K.

BACKGROUND: Among teenagers and young adults, non-suicidal self-injury (NSSI) is highly prevalent and is closely related to suicide and mental disorders. However, existing assessment tools do not comprehensively cover the four stages of NSSI (idea-gesture-plan-behavior) and have limitations in cultural adaptability, assessment completeness, or clinical practicability. To date, few unified tools can simultaneously assess both suicide and NSSI within a single severity framework. METHODS: Of 2558 participants who completed the initial prescreening, those with a positive history were further assessed for data quality; 295 met the inclusion criteria and comprised the final analytic sample (mean age = 17.96 years; 56.61% female). Psychometric properties were assessed using internal consistency, confirmatory factor analysis (CFA), criterion-related validity, and expert-rated content validity. RESULTS: STBI24K demonstrated excellent internal consistency (α = 0.89) and content validity (S-CVI/Ave = 0.993). CFA supported the eight-factor structure of the STBI24K (χ2/df = 0.87, CFI = 1, TLI = 1.001, RMSEA = 0, SRMR = 0.08). Total score was significantly correlated with depression (r = 0.39, p < 0.001) and anxiety (r = 0.30, p < 0.001). DISCUSSION: The STBI24K is a new self-report tool developed in China that can quickly assess the stage and severity of suicide and NSSI, based on a unified four-stage continuum framework. With strong psychometric properties, it shows potential for use in clinical settings. Future research should validate its psychometric properties in diverse populations and examine predictive validity.