Objective: The Interpersonal-Psychological Theory of Suicide (IPTS) posits two constructs (thwarted belongingness (TB) and perceived burdensomeness (PB)) contribute to suicide ideation. These constructs are typically measured by the Interpersonal Needs Questionnaire (INQ); however, available INQ versions have demonstrated poor psychometric properties with youth. This study examined the INQ using Item Response Theory (IRT) to refine and reduce the scale for clinically depressed and suicidal youth. Methods: Participants were 378 youth (Age M (SD) = 14.78 (1.41), 82.54% female) who completed the INQ. The INQ contains 25 items across two subscales (i.e., TB and PB) rated on a 7-point Likert-type scale. Rating scale performance, dimensionality, model fit, and instrument-level statistics were examined using IRT methodology. Post hoc analyses were performed to further reduce the scale. Results: The INQ was reduced from 25 to 10 items (five per subscale), and response options were refined to four choices. Correlations between original and IRT-refined items were large (r =.97 for PB; r =.98 for TB). Additional item-level (e.g., fit, difficulty) and instrument-level (e.g., dimensionality) characteristics were examined. Conclusions: The newly refined INQ resulted in improved scale reliability and validity. The psychometrically improved INQ can assist clinicians and researchers identify adolescents at risk of experiencing suicide ideation.
ASJC Scopus subject areas
- Clinical Psychology
- Public Health, Environmental and Occupational Health
- Psychiatry and Mental health