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

Christina L Winters; Luciano Giromini; Trevor J Crawford; Francesca Ales; Donald J Viglione; Lara Warmelink

doi:10.1080/13218719.2020.1767720

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

Psychiatr Psychol Law. 2020 Jun 2;28(2):235-254. doi: 10.1080/13218719.2020.1767720. eCollection 2021.

Authors

Christina L Winters¹, Luciano Giromini², Trevor J Crawford¹, Francesca Ales², Donald J Viglione³, Lara Warmelink¹

Affiliations

¹ Department of Psychology, Lancaster University, Lancaster, UK.
² Department of Psychology, University of Turin, Torino, Italy.
³ California School of Professional Psychology, Alliant International University, San Diego, CA, USA.

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