Thwarted belongingness as a predictor of suicidal ideation: A question of operationalization?

• Reconsidering the role of thwarted belongingness in suicide theories may be needed • Decent psychometric properties and support for unidimensionality of the German TBS • As a single predictor TBS predicted suicidal ideation better than the INQ subscale • Rather weak link of TB and suicidal ideation, regardless of operationalization The Interpersonal Theory of Suicide (ITS) posits that thwarted belongingness (TB), perceived burdensomeness (PB), and hopelessness about the unchangeability of both states predict suicidal ideation, with TB often being a weaker predictor compared to PB. This study evaluates the German version of the Thwarted Belongingness Scale (TBS) as an alternative to the Interpersonal Needs Questionnaire (INQ) for operationalizing TB. 411 participants (75.4% female; M age = 29.57; SD age = 11.20) completed an online survey. Factorial validity of the TBS was examined using confirmatory factor analysis. Internal consistency and convergent validity were investigated. Hierarchical linear regression analyses compared TBS and INQ in predicting suicidal ideation, including PB and the interaction of TB×PB as predictors. The TBS demonstrated excellent internal consistency (Cronbach’s α = .95), good fit indices, and convergent validity. Both TBS and INQ significantly predicted suicidal ideation, but no interaction effect of TB×PB was found. PB was a significantly stronger predictor of suicidal ideation than TB, regardless of TB measure used. The TBS showed solid psychometric properties and may be a suitable alternative to the INQ for measuring TB. However, TB remains a weaker predictor of suicidal ideation compared to PB, regardless of operationalization, suggesting the need to reassess the role of TB in suicide theories.