Children and young people with acquired brain injury (ABI) commonly experience long-term emotional, behavioural, and participation difficulties that can affect quality of life for both them and their families. Parents and caregivers also often experience high levels of stress and reduced wellbeing. Despite these needs, family-centred psychological interventions remain limited. Acceptance and Commitment Therapy (ACT) is a values-focused cognitive-behavioural approach designed to increase psychological flexibility and has shown promise for children with long-term health conditions and for parents of children with ABI, but it has not been directly evaluated as a joint therapeutic approach for children with ABI and their parents.

This study (Family CARE-ABI) evaluates the feasibility, acceptability, and preliminary effectiveness of delivering ACT simultaneously to a young person aged 11-18 with an ABI and their parent/guardian. Up to six dyads will be recruited. The study uses a non-concurrent, multiple-baseline, single-case experimental design in which dyads are randomised to begin a 12-week ACT intervention after either a 3- or 4-week baseline period. Sessions (up to 12, one hour each) are delivered via Microsoft Teams by a trainee clinical psychologist under specialist supervision. Therapy integrates the DNA-V model of ACT-developed for young people-with ABI-specific psychoeducation and skills practice tailored to each dyad's needs.

Outcome measures include mental health and wellbeing (Outcome Rating Scale), psychological flexibility (CompACT or AFQ-Y8), symptoms of anxiety and depression (GAD-7, PHQ-9, or RCADS-25), community participation (CASP/CASP-Y), and needs after ABI (MANTIC). Measures are collected at baseline, post-intervention, and 12-week follow-up, with weekly wellbeing ratings throughout participation. Therapeutic alliance (SRS) is obtained after each intervention session. All dyads will also take part in separate qualitative interviews exploring their experiences of the intervention and its impact.

Safety is closely monitored, including assessment of distress, adverse events, and any safeguarding concerns. Participation is voluntary, and dyads may withdraw at any time without affecting usual care. Data are stored securely and anonymised for analysis.

The study aims to generate early evidence regarding whether family-centred ACT may support psychological wellbeing, flexibility, and participation for young people with ABI and their parents, and to inform future intervention development and larger-scale trials.

Inclusion Criteria Both the CYP-ABI and parent participants must meet the inclusion criteria to be recruited to the study.

CYP-ABI participant inclusion criteria include:

• Aged 11 to 18 years at time of recruitment.
• Living at home with parent/guardian.
• Received treatment for an ABI.
• Have sufficient cognitive ability to engage with therapy sessions.
• Has capacity to provide verbal or written informed consent (aged 16 and above) or assent (aged 15 and younger).
• Has the ability to speak sufficient English to understand and engage with the therapeutic and research materials
• Consents for parent/guardian participant involvement in study.

Parent participant inclusion criteria include:

• Aged > 18 at time of recruitment. There is no upper age limit.
• Has the ability to speak sufficient English to understand and engage with the therapeutic and research materials
• Has capacity to provide verbal or written informed consent for self and CYP participant.

Exclusion Criteria:

CYP-ABI and parent participant exclusion criteria include:

• CYP or parent participants are currently accessing or have accessed structured psychological intervention within 6 months of study recruitment.