Psychometric and factorial validity of the International Adjustment Disorder Questionnaire (IADQ) in an Italian sample: A validation and prevalence estimate study.

Introduction: Adjustment disorder (AjD) is a is a maladaptive emotional or behavioural reaction to a stressful event or change in a person's life. Compared to other previously validated tools, the International Adjustment Disorder Questionnaire (IADQ) stands out as one of the most reliable and handy one for AjD. Since no homologous instrument exists now, in this study, we aimed to validate an Italian version of the IADQ.

Methods: Twenty-one thousand two hundred and six subjects (80.4% females) during the initial stages of the SARS-CoV-2 pandemic were recruited. We conducted a confirmatory factor analysis (CFA), testing two latent models, a monofactorial and a bifactorial one. Concurrent validity by correlating the total and the two factors' scores with measures of depression, anxiety and post-traumatic stress was then estimated. We finally estimated the rates of AjD among the population, and a binary logistic regression was conducted to analyse the predictors of such disorder.

Results: CFA showed a bifactorial validity, with both excellent incremental and comparative fit indices. The IADQ scores correlated strongly with symptoms of depression, anxiety and stress. In the Italian sample, the prevalence of probable AjD was 8.23%. Female gender, being engaged, widowed and having COVID-19-related stressors resulted as significant independent risk factors for AjD.

Conclusions: IADQ is an easy-to-use, brief and psychometrically sound self-report measure for AjD. Thus, it may be considered a reliable tool for both research and clinical settings. To the best of our knowledge, our study reported for the first time the prevalence of AjD during COVID-19 pandemic.