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 (<i>F</i><sub>822.9</sub>=0.09; 95% CI 0.090-0.277; <i>P</i>=.32), and OASIS and the Panic Disorder Severity Scale (<i>F</i><sub>596.6</sub>=–0.02; 95% CI –0.108 to –0.065; <i>P</i>=.63) from first the session to the last one, while the 7-item Generalized Anxiety Disorder scale (<i>F</i><sub>4345.8</sub>=–0.06; 95% CI –0.109 to –0.017; <i>P</i>=.007), Penn State Worry Questionnaire (<i>F</i><sub>4270.8</sub>=–0.52; 95% CI –0.620 to –0.437; <i>P</i><.001), and Social Phobia Inventory (<i>F</i><sub>862.1</sub>=–0.39; 95% CI –0.596 to –0.187; <i>P</i><.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.