Validation of the Polish version of the International Adjustment Disorder Questionnaire (IADQ) in a Community Sample of Young Adults

Adjustment Disorder (AjD), classified in ICD-11 as a stress-related condition, is common and often linked to anxiety symptoms. Validated tools for AjD assessment in non-English-speaking populations are limited. This study aimed to validate the Polish version of the International Adjustment Disorder Questionnaire (IADQ) and examine its clinical relevance. A representative sample of 2,418 Polish young adults (18–29) completed the IADQ, Perceived Stress Scale (PSS-10), Mental Health Continuum–Short Form (MHC-SF), and Personality Inventory for ICD-11 (PiCD). Confirmatory factor analysis tested the two-factor structure and gender invariance. Reliability, validity, and regression analyses were conducted. The two-factor model (Preoccupation, Failure to Adapt) showed excellent fit (CFI = 0.988, RMSEA = 0.080) and gender invariance. Internal consistency was high (α = 0.92 total). AjD symptoms correlated strongly with perceived stress (r = .60) and negative affect (r = .52), and inversely with well-being (r = − .30). Known-groups validity indicated higher symptoms among women and those with multiple stressors. Regression analyses confirmed negative affect as a positive predictor and well-being as a negative predictor of AjD severity. Applying ICD-11 criteria, 34.7% met probable AjD. The Polish IADQ demonstrates strong psychometric properties and clinical utility for screening stress-related disorders. The tool offers valuable opportunities for early identification and intervention in stress-related psychopathology.