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

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 (OLIFE) under standard instruction. The IOP–29’s feigning scale (FDS) showed excellent validity in discriminating honest responding from feigned schizophrenia (AUC ¼ .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.