Further validation of the IDAS: Evidence of Convergent, Discriminant, Criterion, and Incremental Validity

David Watson, University of Iowa
Michael W. O'Hara, University of Iowa
Michael Chmielewski, University of Iowa
Elizabeth A. McDade-Montez, University of Iowa
Erin Koffel, University of Iowa
Kristin Naragon, University of Iowa
Scott Stuart, University of Iowa

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Abstract

We explicated the validity of the Inventory of Depression and Anxiety Symptoms (IDAS; Watson et al., 2007) in two samples (306 college students, and 605 psychiatric patients). The IDAS scales showed strong convergent validity in relation to parallel interview-based scores on the Clinician Rating version of the IDAS (IDAS-CR); the mean convergent correlations were .51 and .62 in the student and patient samples, respectively. With the exception of Well-Being, the scales also consistently demonstrated significant discriminant validity. Furthermore, the scales displayed substantial criterion validity in relation to DSM-IV mood and anxiety disorder diagnoses in the patient sample. We identified particularly clear and strong associations between (a) major depression and the IDAS General Depression, Dysphoria and Well-Being scales; (b) panic disorder and IDAS Panic; (c) posttraumatic stress disorder and IDAS Traumatic Intrusions; and (d) social phobia and IDAS Social Anxiety. Finally, in logistic regression analyses, the IDAS scales showed significant incremental validity in predicting several DSM-IV diagnoses when compared against the Beck Depression Inventory-II (Beck, Steer, & Brown, 1996) and Beck Anxiety Inventory (Beck & Steer, 1990).