1 Cyberpsychology Laboratory and Department of Psychoeducation and Psychology, Université du Québec en Outaouais, Campus de Saint-Jérôme, 5 rue Saint-Joseph, Saint-Jérôme, QC, J7Z 0B7, Canada. christophe.maiano@uqo.ca.
2 Substantive-Methodological Synergy Research Laboratory, Department of Psychology, Concordia University, Montreal, Canada. christophe.maiano@uqo.ca.
3 Substantive-Methodological Synergy Research Laboratory, Department of Psychology, Concordia University, Montreal, Canada.
4 Department of Psychoeducation and Psychology, Université du Québec en Outaouais, Campus de Saint-Jérôme, Saint-Jérôme, Canada.
5 Département de Psychopédagogie et d'andragogie, Université de Montréal, Montreal, Canada.
6 School of Education, Translational Health Research Institute, Western Sydney University, Sydney, Australia.
7 Institute for Positive Psychology and Education, Australian Ca

The objective of the study was to validate adapted versions of the Glasgow Anxiety Scale for people with Intellectual Disabilities (GAS-ID) simultaneously developed in English and French. A sample of 361 youth with mild to moderate intellectual disability (ID) (M = 15.78 years) from Australia (English-speaking) and Canada (French-speaking) participated in this study. The results supported the factor validity and reliability, measurement invariance (between English and French versions), a lack of differential items functioning (as a function of youth's age and ID level, but not sex in the English-Australian sample), temporal stability (over one year interval), and convergent validity (with global self-esteem and school loneliness) of a bi-factor exploratory structural equation modeling representation of the GAS-ID. The present study supports the psychometric properties of the English-Australian and French-Canadian versions of the adapted GAS-ID.