The Overall Anxiety Severity and Impairment Scale as an Outcome Measure in Internet-Delivered Cognitive Behavioral Therapy for Anxiety Disorders: Observational Study

Background: Internet-delivered cognitive behavioral therapy (iCBT) is effective in the treatment of anxiety disorders. iCBT clinical trials use relatively long and time-consuming disorder-specific rather than transdiagnostic anxiety measurements. Overall Anxiety Severity and Impairment Scale (OASIS) is a brief self-report scale that could offer a universal, easy-to-use anxiety measurement option in disorder-specific and transdiagnostic iCBT programs. Objective: We aimed to investigate relationships between OASIS and disorder-specific instruments in iCBT. We expected these relationships to be positive. Methods: We investigated patients in original nationwide iCBT programs for generalized anxiety disorder (GAD), obsessive-compulsive disorder, panic disorder, and social anxiety disorder, which were administered by Helsinki University Hospital, Finland. In each program, anxiety symptoms were measured using both disorder-specific scales (the 7-item Generalized Anxiety Disorder scale, Penn State Worry Questionnaire, revised Obsessive-Compulsive Inventory, Panic Disorder Severity Scale, and Social Phobia Inventory) and by OASIS. A general linear model for repeated measures (mixed models) and interaction analysis were used for investigating the changes and relationships in the mean scores of OASIS and disorder-specific scales from the first session to the last one. Results: The main effect of linear mixed models indicated a distinct positive association between OASIS and disorder-specific scale scores. Interaction analysis demonstrated relatively stable associations between OASIS and the revised Obsessive-Compulsive Inventory (F-822.9=0.09; 95% CI 0.090-0.277; P=.32), and OASIS and the Panic Disorder Severity Scale (F-596.6=-0.02; 95% CI -0.108 to -0.065; P=.63) from first the session to the last one, while the 7-item Generalized Anxiety Disorder scale (F-4345.8=-0.06; 95% CI -0.109 to -0.017; P=.007), Penn State Worry Questionnaire (F-4270.8=-0.52; 95% CI -0.620 to -0.437; P<.001), and Social Phobia Inventory (F-862.1=-0.39; 95% CI -0.596 to -0.187; P<.001) interrelated with OASIS more strongly at the last session than at the first one. Conclusions: OASIS demonstrates clear and relatively stable associations with disorder-specific symptom measures. Thus, OASIS might serve as an outcome measurement instrument for disorder-specific and plausibly transdiagnostic iCBT programs for anxiety disorders in regular clinical practice.

Automated summary

This study aimed to investigate the relationship between the Overall Anxiety Severity and Impairment Scale (OASIS) and disorder-specific instruments in internet-delivered cognitive behavioral therapy (iCBT) for anxiety disorders. The results showed a clear and relatively stable association between OASIS and disorder-specific symptom measures, suggesting that OASIS could be used as an outcome measurement instrument in both disorder-specific and transdiagnostic iCBT programs for anxiety disorders.