An Inventory of Problems–29 (IOP–29) study investigating feigned schizophrenia and random responding in a British community sample

Abstract

Compared to other Western countries, malingering research is still relatively scarce in the United Kingdom, partly because only a few brief and easy-to-use symptom validity tests (SVTs) have been validated for use with British test-takers. This online study examined the validity of the Inventory of Problems–29 (IOP–29) in detecting feigned schizophrenia and random responding in 151 British volunteers. Each participant took three IOP–29 test administrations: (a) responding honestly; (b) pretending to suffer from schizophrenia; and (c) responding at random. Additionally, they also responded to a schizotypy measure (O-LIFE) under standard instruction. The IOP–29’s feigning scale (FDS) showed excellent validity in discriminating honest responding from feigned schizophrenia (AUC = .99), and its classification accuracy was not significantly affected by the presence of schizotypal traits. Additionally, a recently introduced IOP–29 scale aimed at detecting random responding (RRS) demonstrated very promising results.

Keywords:

• British
• feigning
• Inventory of Problems
• IOP–29
• malingering
• O-LIFE
• Oxford–Liverpool Inventory of Feelings and Experiences
• random responding
• schizophrenia
• schizotypy

Ethical standards

Declaration of conflicts of interest

Luciano Giromini and Donald J. Viglione declare that they own a share in the corporate (LLC) that possesses the rights to the Inventory of Problems.

Christina L. Winters has declared no conflicts of interest

Trevor J. Crawford has declared no conflicts of interest

Francesca Ales has declared no conflicts of interest

Lara Warmelink has declared no conflicts of interest

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Notes

1 For access to the code, please contact author Lara Warmelink at l.https://[email protected]