El Inventory of Depression and Anxiety Symptoms II (IDAS-II)propiedades psicométricas, interpretación de las puntuaciones y utilidad clínica de la versión en castellano

Abstract

Internalizing disorders, such as depression and anxiety, are the most prevalent and disabling mental disorders worldwide (e.g., WHO, 2017). The symptoms of these disorders can be assessed, from a dimensional perspective and consistent with the Hierarchical Taxonomy of Psychopathology (HiTOP; Kotov et al., 2017), with the Inventory of Depression and Anxiety Symptoms (IDAS; Watson et al., 2012). The IDAS-II is among the five most widely used and studied self-report measures of depression in current research (Klein, 2023), as it allows for a transdiagnostic assessment covering the symptomatology of different disorders (e.g., depression, anxiety, bipolar disorder, obsessive-compulsive disorder, and post-traumatic stress disorder), and has norms and cutoffs that extend the clinical utility of the instrument (Nelson et al., 2018; Stasik-O’Brien et al., 2019). However, the psychometric properties of the Spanish version of the instrument have not yet been examined.The general aim of this doctoral dissertation is to study the psychometric properties of the IDAS-II adapted to the Spanish context and language by providing evidence of reliability and validity, developing norms and cutoffs for interpreting scores, and examining the clinical utility of the measure in patients with mental disorders. This general aim is addressed in four papers that present the results of this doctoral dissertation. The first paper provides psychometric evidence supporting the use of the IDAS-II in the Spanish context, with adequate values of internal consistency, stability, and evidence of convergent and discriminant validity. In addition, the results show for the first time that the internal structure of the IDAS-II is consistent with the conceptualization of the instrument (Irak & Albayrak, 2020; Watson et al., 2012; Wester et al., 2022) as well as with the HiTOP model (Kotov et al., 2017). The second paper applies empirical network analysis to shed light on the relationships between internalizing symptoms and identifying symptoms that could contribute to comorbidity, one of the main challenges in clinical practice (e.g., Amerio et al., 2016; Ludmir & Small, 2018). The results suggest that Dysphoria could be a relevant symptom in the initiation and maintenance of depressive and anxiety disorders, while Mania, Panic, Claustrophobia, and (low) Well-Being could contribute to explaining comorbidity between disorders. The third paper provides evidence of the unidimensionality of all IDAS-II scales, which supports the independent use of each scale. In addition, we generate norms that allow the identification of the severity of each symptom considering, for the first time, the sex and age of the individuals. The fourth paper provides clinical cutoffs that allow reliable discrimination between functional and dysfunctional samples, in addition to the cutoffs that allow discrimination between different levels of disability. Using the provided norms and cutoffs, clinicians can develop personalized interventions that focus on the most severe and/or disabling symptoms. Finally, we identify the internalizing symptoms that contribute the most to explaining the disability. Overall, the contributions of this doctoral dissertation facilitate the use of the IDAS-II in the Spanish context, an instrument that allows a precise, detailed, and exhaustive assessment of the internalizing symptomatology associated with emotional disorders. These contributions are framed in national and international guidelines on mental health (e.g., European Commission Decision, 2020; United Nations, 2015), providing a tool that improves the assessment of patients in different stages of the therapeutic process and broadens the scope for action in clinical and research contexts in Spain.