[Interpersonal Problems and their differential indicator function: On the Validity and Clinical Utility of the German...

The present study examines the validity and clinical utility of the German version of the Inventory of Interpersonal Problems (IIP-32) for assessing interpersonal difficulties and their associations with personality functioning, attachment dimensions, and self-perception in a large clinical sample. Interpersonal problems are closely linked to mental health disorders and are often a central focus of psychotherapeutic interventions. Recent findings underscore the importance of interpersonal aspects for understanding and treating mental health disorders, particularly personality disorders, especially through a dimensional perspective as emphasized in DSM-5 and ICD-11.Using data from 7,507 patients in a psychosomatic rehabilitation clinic, we evaluated the internal consistency and construct validity of the IIP-32, as well as its correlations with key variables such as attachment avoidance, attachment anxiety, and structural deficits in personality functioning, measured with the OPD-SFK and ECR-RD12. Additionally, the circumplex structure of the IIP-32 was assessed through correlation-based analyses with the SASB.Overall interpersonal distress correlated strongly with structural deficits in personality functioning (r=0.71), attachment anxiety (r=0.45), and attachment avoidance (r=0.38). Attachment avoidance showed strong associations with hostile-withdrawing and socially avoidant behavior (r=0.50), while no relevant associations with friendly-dominant interpersonal problems were found. The IIP-32 primarily captured submissive-avoidant interpersonal patterns, which were linked to deficits in personality structure. SASB analyses confirmed the circumplex structure of the IIP-32 (R²>0.80) and its alignment with the dominance and affiliation axes. High correlations with structural deficits support the convergent validity, while differentiated associations with attachment measures and interpersonal profiles in the SASB model indicate discriminant validity.The findings demonstrate that the IIP-32 is a reliable instrument for the differentiated assessment of interpersonal problems. The combination of analyses with the OPD-SFK, ECR-RD12, and SASB provides evidence for the structural validity and clinical utility of the IIP-32, both for diagnosing interpersonal distress and identifying specific behavioral patterns that can be addressed in psychotherapy.