Telehealth-delivered naturalistic developmental behavioural intervention with and without caregiver acceptance and commitment therapy for autistic children and their caregivers: protocol for a multi-arm parallel group randomised clinical trial.

Introduction: Timely access to early support that optimises autistic children's development and their caregiver's mental health is critical. Naturalistic developmental behavioural interventions (NDBIs) and acceptance and commitment therapy (ACT) are evidence-based supports that can enhance child learning and behaviour, and adult well-being, respectively. The traditional face-to-face delivery of these approaches is resource intensive. Further, little is known about the benefit of parallel child-focused and caregiver-focused supports. The aims of this trial are to evaluate the effectiveness and social validity of telehealth-delivered, caregiver-implemented, child-focused NDBI and caregiver-focused ACT when delivered alone and in parallel, on autistic children's social communication and caregiver well-being.

Methods And Analysis: The study will use a randomised, single-blind clinical trial with three parallel arms: NDBI; ACT and ACT+NDBI. We will recruit a minimum of 78, 2-5-year-old autistic children and their families throughout Aotearoa New Zealand. Support will be delivered over 13 weeks using a combination of culturally enhanced web-based modules and online group coaching. Primary outcome variables include children's social communication/engagement with their caregiver as well as caregiver stress and will be evaluated using a repeated measures multivariate analysis of variance. Outcome variables are assessed at baseline (before randomisation), immediately postparticipation and at 3-month follow-up.

Ethics And Dissemination: The trial is approved by the Health and Disability Ethics Committee (2022 FULL 12058). The findings of this trial will be disseminated through peer-reviewed journals and national and international conference proceedings regardless of the magnitude/direction of effect. Additionally, data will be shared with stakeholder groups, service providers and health professionals.

Trial Registration Number: Australian New Zealand Clinical Trials Registry (ACTRN12622001134718).