Brief-intensive CBT Versus Once-weekly CBT in Anxiety-related Disorders

Area Under the health and disability Curve at 12 months

The 'area under the curve' for health and disability is based on the 36-item self-report World Health Organisation Disability Assessment Schedule (WHODAS 2.0). The WHODAS 2.0 captures the level of functioning in six domains of life: Cognition, Mobility, Self-care, Getting along, Life activities, Participation. Possible total scores of the items across all domains range 0 - 100. Lower scores indicate less disability.

Time frame: baseline, 2 weeks, 4 weeks, 2 months, 3 months, 6 months, 12 months

Change from baseline in severity of anxiety symptoms at post-treatment

Severity of anxiety-related disorder, measured with the following disorder-specific severity questionnaires: the 24-item Liebowitz Social Anxiety Scale self-report version, the 7-item Panic Disorder Severity Scale self-report version, the 28-item Mobility Inventory, the 16-item Penn State Worry Questionnaire, the 10-item Yale-Brown Obsessive Compulsive Scale self-report version, the 20-item PTSD checklist for the DSM-5, or the 14-item Whitely Index. Higher scores indicate higher symptom severity. Z-scores will be calculated from individual scores for group-level analyses.

Time frame: baseline and 3 or 6 months

Change from baseline in severity of anxiety symptoms at 3 months

Severity of anxiety-related disorder, measured with the following disorder-specific severity questionnaires: the 24-item Liebowitz Social Anxiety Scale self-report version, the 7-item Panic Disorder Severity Scale self-report version, the 15-item Fear Questionnaire, the 16-item Penn State Worry Questionnaire, the 10-item Yale-Brown Obsessive Compulsive Scale self-report version, the 20-item PTSD checklist for the DSM-5, or the 14-item Whitely Index. Higher scores indicate higher symptom severity. Z-scores will be calculated from individual scores for group-level analyses.

Time frame: baseline and 3 months

Change from baseline in severity of anxiety symptoms at 12 months

Severity of anxiety-related disorder, measured with the following disorder-specific severity questionnaires: the 24-item Liebowitz Social Anxiety Scale self-report version, the 7-item Panic Disorder Severity Scale self-report version, the 28-item Mobility Inventory, the 16-item Penn State Worry Questionnaire, the 10-item Yale-Brown Obsessive Compulsive Scale self-report version, the 20-item PTSD checklist for the DSM-5, or the 14-item Whitely Index. Higher scores indicate higher symptom severity. Z-scores will be calculated from individual scores for group-level analyses.

Time frame: baseline and 12 months

Change from baseline in severity of depressive symptoms at post-treatment

Severity of depressive symptoms are measured with the 30-item Inventory for Depressive Symptomatology self-report questionnaire. Higher scores indicate higher symptom severity.

Time frame: baseline and 3 or 6 months

Change from baseline in severity of depressive symptoms at 3 months

Severity of depressive symptoms are measured with the 30-item Inventory for Depressive Symptomatology self-report questionnaire. Higher scores indicate higher symptom severity.

Time frame: baseline and 3 months

Change from baseline in severity of depressive symptoms at 12 months

Severity of depressive symptoms are measured with the 30-item Inventory for Depressive Symptomatology self-report questionnaire. Higher scores indicate higher symptom severity.

Time frame: baseline and 12 months

Remission rates from anxiety-related disorder at post-treatment

Remission of diagnoses of anxiety-related disorders is assessed using the Mini International Neuropsychiatric Interview - Simplified for DSM-5, Dutch version 1.1 (Overbeek \& Schruers, 2019).

Time frame: 3 or 6 months

Remission rates from anxiety-related disorder at 12 months

Remission of diagnoses of anxiety-related disorders is assessed using the Mini International Neuropsychiatric Interview - Simplified for DSM-5, Dutch version 1.1 (Overbeek \& Schruers, 2019).

Time frame: 12 months

New-onset anxiety-related or depressive disorder post-treatment

The new onset of anxiety-related or depressive disorder between baseline and post-treatment is assessed using the Mini International Neuropsychiatric Interview - Simplified for DSM-5, Dutch version 1.1 (Overbeek \& Schruers, 2019)

Time frame: baseline, 3 or 6 months

New-onset anxiety-related or depressive disorder at 12 months

The new onset of anxiety-related or depressive disorder between baseline and post-treatment is assessed using the Mini International Neuropsychiatric Interview - Simplified for DSM-5, Dutch version 1.1 (Overbeek \& Schruers, 2019)

Time frame: 12 months

Productivity costs over 12 months

Productivity losses are assessed using the iMTA Productivity Cost Questionnaire (iPCQ). The iPCQ is a 12-item self-report questionnaire including three modules measuring productivity losses of paid work due to 1) absenteeism and 2) presenteeism and productivity losses related to 3) unpaid work in the past 3 months.

Time frame: 3months, 6months, 12 months

Medical costs over 12 months

Medical costs from a mental health care perspective are assessed using the iMTA Medical Cost Questionnaire (iMCQ). The iMCQ is a 23-item self-report questionnaire, which apart from some general questions include questions on medical consumption from different healthcare providers in the past 3 months.

Time frame: 3months, 6months, 12 months

Change from baseline in health-related quality of life over 12 months

Quality of life is measured using the EQ-5D-5L. The EQ-5D-5L scores (reflecting the level of perceived problems on the dimensions of mobility, self-care, usual activities, pain/discomfort and anxiety/depression) are used to calculate utilities using the Dutch tariff. Quality Adjusted Life Years are calculated using linear interpolation between time points. Higher QALY scores indicate more improvement in quality of life.

Time frame: baseline, 2 weeks, 4 weeks, 2 months, 3 months, 6 months, 12 months

Drop-out rates at post-treatment

Percentage of patiënts who missed more than 25% of CBT sessions.

Time frame: 3 or 6 months

Patient satisfaction at post-treatment

The 8-item Client Satisfaction Questionnaire (CSQ-8) measures overall satisfaction of the patient with health and human services. Each item on the CSQ-8 is scored from 1 (low satisfaction) to 4 (high satisfaction), possible total scores ranging 8-32.

Time frame: 3 or 6 months

Negative effects of psychotherapy

The 21-item Inventory for the Assessment of Negative Effects of Psychotherapy (INEP) is a self-report instrument for assessing negative effects of psychotherapy from the patient's perspective. The negative effects cover 7 domains: Intrapersonal Change, Intimate Relationships, Stigmatization, Emotions, Workplace, Family and Friends, and Therapeutic Malpractice. The INEP items are answered using a 4-stage response format (0 = "disagree/not applicable"; 3 = "fully agree").

Time frame: 3 or 6 months