The German version of the Interpersonal Needs Questionnaire (INQ)--Dimensionality, psychometric properties and population-based norms.

PURPOSE: The Interpersonal Needs Questionnaire (INQ) assesses the two interpersonal constructs perceived burdensomeness (PB) and thwarted belongingness (TB) that lead to suicidal ideation, according to the interpersonal theory of suicide (IPTS). The present study investigates dimensionality and psychometric properties of the German version of the INQ in a population-based representative sample and delivers norm values. METHODS: The German INQ as well as measures of depression and past suicidality were administered to a population-based representative sample of the German general population (n=2513) to analyze its dimensionality and construct validity by confirmatory factor analysis and correlational analysis. RESULTS: Results of the confirmatory factor analysis were in line with the assumption of two-dimensionality of the INQ. The two subscales showed very good internal consistencies (α ≥ 0.89) as well as correlations with depression and suicidality that indicate convergent validity. There were no gender effects but slight age effects in the scores of both subscales. Population-based norms are provided. LIMITATIONS: Convergent validity was solely examined with measures of depression and suicidal thoughts instead of further suitable constructs like loneliness and social support. Divergent validity was not investigated in the study. CONCLUSION: The German version of the INQ shows good psychometric properties making it a promising tool for assessing PB and TB. The provided norms enable researchers to compare INQ scores of their samples with reference values of a population-based representative sample.