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ABSTRACT
Introduction: Grandiose delusions (GD) are frequent in some clinical populations and can also be found in a minority of the general population. Despite the high prevalence, no specific tools have been developed to assess GD extensively. The present study aimed to develop and validate a specific questionnaire: the Bergen-Montpellier grandiose ideas questionnaire (B-MGI).
Method: To begin with, an over-inclusive item pool was generated and subjected to exploratory factor analysis to identify the items to keep and to discard. This was done using a large sample of 183 participants from the general population. A second sample of 181 healthy participants was then used to confirm the 4-factor structure of the B-MGI.
Results: Significant, albeit weak, correlations were found between the B-MGI and positive psychotic symptoms, providing initial support for convergent validity. Moreover, the B-MGI was poorly related to negative psychotic symptoms, supporting the discriminant validity of the B-MGI.
Conclusion: The B-MGI is the first self-report measure that targets specifically GD. The questionnaire demonstrated good preliminary psychometric properties. Future studies should explore further the psychometric properties of the B-MGI.
Author Contributors
Both CB and JL authors contributed to the design of the study and wrote the protocol. JL and CL undertook the statistical analysis, and CB wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.
Acknowledgments
We would like to thank Stéphane Raffard and Frank Larøi for their feedback on our first version of the scale, and the psychiatrists and psychologists who helped us to generate items for the B-MGI.
Disclosure Statement
Authors have no conflict of interest to disclose.