Objective: We report on the validation of the Norwegian version of the Inventory of Problems-29 (IoP-29) using an experimental simulation setup with honest responders and responders feigning depression. Method: The sample consisted of 275 participants recruited by convenience by spreading invitational links to participate in the study on social media. They were randomly assigned to either an experimental simulation or an honest condition with the IoP-29. Participants in both conditions were asked to confirm whether they had followed the instructions or not. The honest respondents (n = 138) were asked to respond to the IoP-29 as honestly as they could, whereas the experimental simulators (n = 137) were told to simulate depression based on a case vignette and descriptions of depressive symptoms. Results: We found that participants in the simulation group scored significantly higher than the control group (d = 2.39, p < .000). We found no significant effects from age, gender, or education on the resulting scores. Area under the curve (AUC) for IoP-29 was .94 (SE = .01), meaning a good ability to separate the two conditions. The cutoff for the IoP-False Disorder Score ≥.50 yielded sensitivity = .77, specificity = .93, positive predictive power = .91, negative predictive power = .81, and an overall correct classification = .85. Conclusions: The Norwegian version of IoP-29 demonstrated good validity in discriminating between experimental simulators of depression and a nonclinical control group. Public Significance StatementOur study shows that the Norwegian translation of Inventory of Problems-29 can effectively discriminate between honest nonclinical responders and feigners of depression. This study marks the first step of the validation of the Norwegian IoP-29 version for clinical use.

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