Cross-cultural applicability of the Inventory of Problems–29 (IOP–29): a pre-registered German replication of Akca, Tepedelen, et al. (2023)

Höpfner H, Uysal B, Stemmler M, Akca AY, Giromini L (2025)

Publication Type: Journal article

Publication year: 2025

Journal

Psychiatry Psychology and Law Taylor & Francis (Routledge): STM, Behavioural Science and Public Health Titles / Taylor & Francis

DOI: 10.1080/13218719.2024.2441788

Abstract

Assessing the credibility of psychological problems in forensic evaluations is crucial. The Inventory of Problems–29 (IOP–29) is becoming a valuable symptom validity test (SVT) worldwide and has been validated in over 15 languages. This study evaluates the German IOP–29 and fills a gap by replicating a study of Akca, Tepedelen, et al. We analysed 384 IOP–29 protocols from 128 German-speaking adults (range = 18–87 years) under three conditions: honest, random and feigned responses (post-traumatic stress disorder, PTSD; depression; schizophrenia). Statistical analyses showed that the False Disorder Probability Score (FDS) effectively discriminated between honest and feigned responses (Hedges g = 3.90), with a sensitivity of.91 and a specificity of.95 at an FDS cut-off value of ≥.50. A new index for detecting careless or random responses also showed promising results. This study confirms the utility of the IOP–29 in the German-speaking population and supports its cross-cultural applicability.

Authors with CRIS profile

Mark Stemmler Lehrstuhl für Psychologische Diagnostik, Methodenlehre und Rechtspsychologie

Involved external institutions

Ibn Haldun University (IHU) / İbn Haldun Üniversitesi

Turkey (TR) Maastricht University

Netherlands (NL) University of Turin / Università degli Studi di Torino (UNITO)

Italy (IT)

How to cite

APA:

Höpfner, H., Uysal, B., Stemmler, M., Akca, A.Y., & Giromini, L. (2025). Cross-cultural applicability of the Inventory of Problems–29 (IOP–29): a pre-registered German replication of Akca, Tepedelen, et al. (2023). Psychiatry Psychology and Law. https://doi.org/10.1080/13218719.2024.2441788

MLA:

Höpfner, Henrike, et al. "Cross-cultural applicability of the Inventory of Problems–29 (IOP–29): a pre-registered German replication of Akca, Tepedelen, et al. (2023)." Psychiatry Psychology and Law (2025).

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