Stepped Versus Stratified Care for Anxiety Disorders in Youth

The Clinical Global Impressions - Improvement (CGI-I) Scale is a 1-item measure where a trained interviewer uses all available information about the patient to rate improvement on a 7-point scale: 1 = Very much improved, 2 = Much improved, 3 = Minimally improved, 4 = No change, 5 = Minimally worse, 6 = Much worse, 7 = Very much worse. In this study, improvement on the CGI-I is assessed by comparing the current status of the participant to their baseline condition. In line with previous studies, a score of 1 or 2 on the CGI-I is classified as a treatment response and scores of 3 to 7 as non-response. This binary variable is the primary outcome of the trial.

The Pediatric Anxiety Rating Scale (PARS) is a clinician-rated measure of overall anxiety severity. It includes seven items assessing the number of anxiety symptoms, their frequency, anxiety-related avoidance, anxiety-related distress, physical symptoms of anxiety, family interference, and social interference. In the current study, in accordance with other trials for youth anxiety disorders, the 6-item version of PARS is used which excludes the item assessing number of symptoms. The resulting 6-item scale yields a score of 0 to 30, with higher scores indicating more severe anxiety.

The Diagnostic Interview for Anxiety, Mood, and OCD and Related Neuropsychiatric Disorders - Child and Adolescent Version (DIAMOND-KID) is a semi-structured interview that assesses the most common mental disorders in children and adolescents, including all the anxiety disorders used for inclusion in the present study. The full interview is conducted at baseline and at the 12- and 24-month post-randomization assessments. A shortened version that includes anxiety disorders and major depression is conducted at the 4- and 8-month post-randomization assessments. Data from the DIAMOND-KID will be used to evaluate the proportion who no longer meet diagnostic criteria for [1] their principal baseline anxiety disorder and [2] any anxiety disorder.

The Clinical Global Impressions Scale-Severity (CGI-S) is a single-item measure where a trained assessor makes an overall severity rating of a specific disorder accounting for all available information about the patient, including but not limited to current symptoms, impairment, and general functioning. In this study, in line with previous trials of youth anxiety disorders, the CGI-S is used to rate the overall severity of the patient's anxiety symptoms, irrespective of their association with a specific anxiety disorder.

The Children's Global Assessment Scale (CGAS) is a clinician-rated one-item scale of psychosocial functioning/impairment, ranging from 1 to 100 with higher scores indicating better functioning.

The Revised Children's Anxiety and Depression Scale (RCADS) is a patient- and caregiver-reported questionnaire assessing specific anxiety symptoms and their frequency. The original version includes 47 items. In the present study, we use the 30-item version, which maintains the factor structure of the original version and demonstrates conserved psychometric properties. The RCADS has shown adequate psychometric properties in several studies, including in Swedish youth, and is an internationally recommended measure for the assessment of internalizing symptoms in children and adolescents. Both patient- and caregiver-reported versions are used in the study. We will use the subscale that sums all the anxiety symptoms, which ranges from 0 to 60, with higher scores indicating more frequent anxiety symptoms.

The Child Anxiety Life Interference Scale-Revised (CALIS-R) is a patient- and caregiver-reported measure of interference associated with youth anxiety. The measure is an internationally recommended tool for the assessment of interference stemming from anxiety in children and adolescents. The patient-reported version consists of 9 items, each rated on a 0-4 response scale, resulting in a total score of 0 to 36, with higher overall scores indicating more interference. The caregiver-reported version consists of two sub-scales, where one sub-scale assesses interference for the child (9 items; range: 0 to 36) and the other interference for the family (8 items; range: 0 to 32), with higher scores indicating more interference. For the caregiver-reported version, the two sub-scales will be reported separately.

Non-adherence to treatment is defined as completing fewer than six modules of ICBT, attending fewer than six sessions of personalized in-person CBT, or discontinuing/refusing treatment despite clinical judgment indicating it is warranted. An exception to the six-module/session rule is made if treatment is discontinued due to substantial symptom improvement to non-clinical levels, with therapist agreement that further treatment is unnecessary. At 4 months, non-adherence is assessed based on the first course of treatment. At 8 months, it is assessed based on overall adherence across both treatment courses: [0] complete adherence (adhering to all assigned treatments), [1] partial adherence (adhering to one but not all assigned treatments), or [2] full non-adherence (adhering to no assigned treatment).

Adverse events are continuously screened, recorded, and monitored by study personnel and through the patient- and caregiver-reported Adverse Events Questionnaire, which includes 22 predefined events and an open-ended option. Events will be reported as the total number of documented events, ranging from 0 with no defined upper limit.

Health economic evaluations, including the calculation of Incremental Cost-Effectiveness Ratios (ICER) and assessment of willingness-to-accept thresholds, will be performed. The details will be specified in a separate Health Economic Analysis Plan (HEAP) and the planned approach is available in the full study protocol at Open Science Framework (https://osf.io/a9qhw/). These measures will not be used to make inference about the non-inferiority RCT regarding anxiety outcomes.