The expanded version of the Inventory of Depression and Anxiety Symptoms (IDAS-II) is a 99-item self-report measure containing 18 nonoverlapping dimensional scales assessing symptoms of depression, anxiety, and mania. The aim of this study was to develop and validate a German adaptation of the IDAS-II. Participants from a community sample (N = 1,054) completed the IDAS-II (German version). In addition, part of the sample (N = 550) completed a series of additional measures of depression (Patient Health Questionnaire–9, WHO–Five Well-Being Index, Symptom Checklist–90 Revised—Short Version) and anxiety disorders (Generalized Anxiety Disorder Scale–7, Fear of Negative Evaluation Scale–5, Dimensional Obsessive–Compulsive Scale, The International Trauma Questionnaire). We conducted item-level confirmatory factor analyses (CFA) separately for the 15 nonsaturated IDAS-II scales, which confirmed unidimensionality. McDonald’s ω indicated good internal consistency (ω > .8) of all symptom scales except Euphoria (ω = .751) and Ordering (ω = .728). A CFA of the IDAS-II scales, based on exploratory results by Watson et al. (2012), confirmed a three-factor model of “Distress,” “Obsessions/Fear,” and “Positive Mood.” Correlational analyses with additional symptom measures supported the convergent and discriminant validity of the IDAS-II scales. The IDAS-II (German version) allows for a reliable assessment of the severity of depression, anxiety, and bipolar symptoms and is one of the first clinical measures for German-speaking samples that is consistent with the Hierarchical Taxonomy of Psychopathology (HiTOP).

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Estimating individual treatment effects (ITEs) is crucial to personalized psychotherapy. It depends on identifying all covariates that interact with treatment, a challenging task considering the many patient characteristics hypothesized to influence treatment outcome. The goal of this study was to compare different covariate-selection strategies and their consequences on estimating ITEs. A Monte Carlo simulation was conducted to compare stepwise regression with and without cross-validation and shrinkage methods. The study was designed to mimic the setting of psychotherapy studies. No single covariate-selection strategy dominated all others across all factor-level combinations and on all performance measures. The least absolute shrinkage and selection operator showed the most accurate out-of-sample predictions, identified the highest number of true treatment-covariate interactions, and estimated ITEs with the highest precision across the most conditions. Domain backward stepwise regression and backward stepwise regression using Bayesian information criterion were least biased in estimating variance of ITEs across the most conditions.

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The Expanded Version of the Inventory of Depression and Anxiety Symptoms (IDAS-II) is a 99-item self-report measure containing 18 nonoverlapping dimensional scales assessing symptoms of depression, anxiety, and mania. The aim of this study was to develop and validate a German adaptation of the IDAS-II. Participants from a community sample (N = 1054) completed the IDAS-II (German version) and a series of additional measures of depression and anxiety disorders. Item-level confirmatory factor analyses (CFA) confirmed unidimensionality and indicated good internal consistency of most symptom scales. A CFA of the IDAS-II scales based on exploratory results by Watson et al (2012) confirmed a three factor model of Distress, Obsessions/Fear, and Positive Mood. Correlational analyses with additional symptom measures supported convergent and discriminant validity. The IDAS-II (German Version) allows for a reliable assessment of severity of depression, anxiety, and bipolar symptoms, and is one of the first clinical measures for German-speaking samples that is consistent with the Hierarchical Taxonomy Of Psychopathology (HiTOP).