Abstract
According to ontological addiction theory, the root cause of mental suffering is a dysfunctional conceptualisation of the self. Typically, an individual with such a flawed self-concept deems themselves to be intrinsically separate from their surroundings, with their beliefs, choices and behaviours structured in order to reinforce their sense of an independently existing self. The Ontological Addiction Scale (OAS) was developed to measure ontological addiction and demonstrates good psychometric properties for the original version validated in English. The present study aimed to validate a French language version of the OAS. The 24-item OAS was administered to 492 French adults with emotional and/or mood disorders. The French OAS demonstrated good internal consistency (Cronbach's alpha: 0.89) and strong test-retest reliability. We suggest a single-factor structure, aligning with the original English version. The 12-item OAS also showed good internal consistency (Cronbach's alpha: 0.81). Construct validity was confirmed by medium to large correlations with self-esteem, shame, perfectionism and mindfulness. These results support the use of the French OAS in research and clinical practice, offering a robust measure for assessing ontological addiction as well as a dimensional assessment of psychiatric symptoms.