Evaluation of Various Support Intensities of Digital Mental Health Treatment for Reducing Anxiety and Depression in Adults: Protocol for a Mixed Methods, Adaptive, Randomized Clinical Trial

**Background:** Anxiety and depressive disorders are among the most debilitating mental disorders worldwide, with the COVID-19 pandemic increasing their global prevalence to an estimated 246 million people for depression and 374 million for anxiety disorders. Digital mental health (dMH) interventions delivered via the internet in formats such as self-help and therapist-assisted programs have a well-established evidence base and can increase access to care within high-volume, low-intensity treatment models. Adaptive intervention designs, including stepped-care models, use decision rules to alter treatment delivery—typically starting with a low-intensity intervention and augmenting it if a participant does not improve or engage. However, robust studies of adaptive web-based designs are scarce, and no identified clinical trial has investigated a two-stage adaptive design where a program-only dMH condition is augmented with either low or high therapist assistance delivered via video chat. This protocol addresses that gap.

**Methods:** This is a two-stage adaptive, mixed-methods randomized clinical trial conducted in Australia. A target sample of 137 adults (aged ≥18 years, Australian residents, with internet access, able to read and write English, with symptoms or a diagnosis of anxiety or depression) will be recruited. Exclusion criteria include current psychological treatment, moderate-to-severe alcohol/substance use, active psychosis or suicidal intent/plan, unstable bipolar disorder, or unstable medication doses. Screening involves a telephone interview corresponding to DSM-5 criteria and a diagnostic assessment using the Mini International Neuropsychiatric Interview (MINI) 7.0.2 via video chat. Eligible participants receive access to the 8-module Life Flex dMH program (a third-wave transdiagnostic biopsychosocial treatment). On day 15, participants who meet augmentation criteria (not reading the introduction/module 1, symptom deterioration >5 points on PHQ-9 or GAD-7, symptoms remaining in severe range, or non-completion of week 3 questionnaire) are stepped up via block randomization to either low-intensity therapist assistance (one 10-minute weekly video chat session) or high-intensity therapist assistance (one 50-minute weekly video chat session) for up to 7 sessions. Participants who improve or engage remain in the program-only condition. Outcomes are assessed at pre-intervention (week 0), during intervention (weeks 3 and 6), post-intervention (week 9), and 3-month follow-up (week 21). Primary outcomes are anxiety (GAD-7) and depression (PHQ-9). Secondary outcomes include working alliance (WAI-S), health status (AQol), health resources, self-efficacy (BPSES-modified), motivation (CMOTS), usability (System Usability Scale), preferences, and satisfaction. Qualitative data will be collected via semi-structured interviews with participants and therapists. Therapists are provisionally or generally registered psychologists who complete a 14-hour, 5-module web-based training program with a 40-item competency assessment (minimum 80% score). Treatment fidelity is ensured via a treatment manual, random checks of 20% of recorded sessions, and regular supervision.

**Key Results:** Recruitment commenced in November 2020 and was completed at the end of March 2022. Of 240 individuals who registered, 113 (47.1%) were assessed as eligible to commence the dMH intervention. At week 3, 73 of 113 participants (64.6%) met the stepped-care criteria to be augmented with therapist assistance, while 40 (35.4%) remained in the program-only condition. The clinical results are forthcoming and have been accepted for publication in JMIR Publications. The planned primary analysis will use intention-to-treat with mixed model repeated-measures analysis to compare changes in GAD-7 and PHQ-9 scores from pre-intervention to post-intervention (week 9) and follow-up (week 21). Reliable and clinically significant change will be assessed per Jacobson and Traux criteria. Moderation analyses will examine the role of self-efficacy and motivation. Qualitative data will be analyzed using thematic analysis.

**Clinical Implications:** This is the first adaptive mixed-methods trial to compare different intensities of therapist-assisted dMH delivered via video chat for anxiety and depression. If therapist-assisted video chat support proves more effective than program-only support, it would demonstrate the benefit of augmenting dMH with video chat in community mental health. If low and high therapist assistance yield similar outcomes, this would support implementing low-intensity dMH interventions to increase timely community access. The mixed-methods design will provide insights into participant engagement, attrition, and experiences with video chat technology, as well as therapist training and implementation factors. Findings may inform stepped-care models and the wide dissemination of dMH interventions for anxiety and depression.