Development and evaluation of the anxiety disorder diagnostic questionnaire.

A model of anxiety that emphasizes a single common pathology across diagnostic categories is gaining support and influencing nosological and treatment approaches of anxiety disorders. As research in this area continues to grow, a need exists for an assessment tool of the theorized single anxiety pathology that is unbiased toward any particular anxiety diagnosis. The Anxiety Disorder Diagnostic Questionnaire (ADDQ) was developed as a screening tool for the presence of clinical fear and anxiety irrespective of diagnoses. It is a brief four-section index developed to assess fear, anxiety/worry, escape/avoidance behaviors, physiological symptoms, and associated distress and interference. The ADDQ was tested for reliability and validity in two samples: 146 undergraduate students who were given the ADDQ along with a variety of other commonly-used measures of anxiety and 94 outpatients representing a mix of diagnoses (28.2% panic disorder with or without agoraphobia, 44.6% social anxiety disorder, 20.7% generalized anxiety disorder, 3.3% anxiety disorder not otherwise specified, 2.1% obsessive-compulsive disorder, and 1.1% posttraumatic stress disorder). Internal consistency of the instrument was strong, and a one- or two-factor solution was found to be the best fit to the data. Convergent and discriminant validity was also demonstrated. Data from those clinical participants who completed a manualized cognitive-behavioral treatment program indicated a very strong concordance between change on the ADDQ and change in clinician severity ratings from a structured diagnostic interview. The findings offer support for the psychometric validity of the ADDQ in both clinical and nonclinical populations.