Evaluating CBT Bytesize: a mixed-methods feasibility trial of a blended digital CBT intervention for adolescent anxiety and low mood
| ISRCTN | ISRCTN17872625 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN17872625 |
| Secondary identifying numbers | 34434 |
- Submission date
- 28/05/2025
- Registration date
- 04/06/2025
- Last edited
- 08/07/2025
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Mental and Behavioural Disorders
Plain English summary of protocol
Background and study aims
Anxiety is common in children and young people and can affect their daily lives, including school, family, and friendships. CBT Bytesize is a new digital mental health programme designed to make therapy more accessible by combining online self-help tools with support from a therapist. The aim of the study is to test whether CBT Bytesize is easy to use and whether it helps reduce anxiety in young people.
Who can participate?
The study included children and young people aged 8 to 17 who had been referred to a mental health service for anxiety-related difficulties. To take part, they needed to have access to the internet, be able to understand and speak English, and be suitable for a short course of CBT. Clinicians who delivered the CBT Bytesize programme were also invited to take part in focus groups to share their experiences.
What does the study involve?
Young people in the study took part in the CBT Bytesize programme, which included short online learning modules and therapist support, delivered either remotely or in person. Their progress was compared to that of similar young people who had previously received standard online CBT.
Researchers looked at whether anxiety and low mood improved after completing CBT Bytesize. They also examined how many young people continued using the programme and what they thought about it. Feedback from clinicians who delivered the programme was gathered through focus groups and analysed using thematic analysis.
What are the possible benefits and risks of participating?
The programme may help young people manage anxiety more effectively and provide a more flexible way to access therapy. There are minimal risks, but some young people might find it challenging to engage with digital content or talk about difficult feelings.
Where is the study run from?
The study was coordinated by Manchester Metropolitan University and delivered in partnership with Healios Ltd, a digital mental health service provider.
When is the study starting and how long is it expected to run for?
December 2021 to August 2023
Who is funding the study?
The study was jointly funded by Manchester Metropolitan University and Healios Ltd (UK)
Who is the main contact?
Dr Daniela Di Basilio, d.dibasilio@lancaster.ac.uk
Contact information
Public, Scientific, Principal Investigator
Sir John Fisher Drive
Bailrigg
Lancaster
LA1 4YW
United Kingdom
 ORCID ID |
0000-0003-3786-442X |
|---|---|
| Phone | +44 (0)7312255301 |
| d.dibasilio@lancaster.ac.uk |
Public, Scientific
Healios Ltd
4a Tileyard Studios
Tileyard Road
Kings Cross
London
N7 9AH
United Kingdom
| ORCID ID |
0000-0002-2402-3376 |
|---|
Public, Scientific
Healios Ltd
4a Tileyard Studios
Tileyard Road
Kings Cross
London
N7 9AH
United Kingdom
Study information
| Study design | Matched mixed-methods feasibility and usability trial |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Case-control study |
| Study setting(s) | Internet/virtual, Medical and other records, Other therapist office |
| Study type | Diagnostic, Other, Prevention, Screening |
| Participant information sheet | Not available in web format, please use contact details to request a participant information sheet |
| Scientific title | Evaluating CBT Bytesize: a mixed-methods feasibility trial of a blended digital CBT intervention for adolescent anxiety and low mood |
| Study acronym | CBT Bytesize |
| Study objectives | Current study objectives as of 08/07/2025: 1. Estimating enrolment and uptake: Measured as the proportion of eligible young people referred by NHS clinicians who were enrolled in the CBT Bytesize programme. (Target: >30% of those referred engage with the programme) 2. Assessing retention and engagement: Defined as the proportion of enrolled participants who attended at least 75% of the core intervention sessions (i.e. ≥9 out of 12 sessions). (Target: >70% session completion rate) 3. Completeness of outcome measures: Measured by the proportion of participants who completed key clinical outcome measures (RCADS, YP-CORE) at baseline and end-of-study (Target: >80% data completion across timepoints) 4. Acceptability of the intervention: Evaluated through qualitative feedback and user engagement data, including self-reported satisfaction and willingness to recommend the programme. (Target: >80% reporting satisfaction with content and format) 5. Feasibility of trial procedures: Assessed via clinician and service feedback regarding referral, delivery, and data collection processes. (Target: majority positive feedback from participating clinicians and low procedural burden) _____ Previous study objectives: Primary hypothesis: 1. CBT Bytesize will be effective in reducing anxiety symptoms in children and young people (CYP) compared to a matched historical control group receiving treatment as usual (TAU) online CBT. Secondary hypotheses: 1. CBT Bytesize will be feasible and usable for CYP, as demonstrated by adherence to the intervention protocol and positive feedback from participants and clinicians. 2. CYP participating in CBT Bytesize will report positive therapeutic experiences, including perceived support and satisfaction with the hybrid delivery model (app + therapist interaction). 3. Clinicians delivering CBT Bytesize will find the model acceptable and manageable, with insight into its adaptability, potential benefits, and challenges in routine practice. 4. Therapeutic improvements (e.g., anxiety reduction) will be maintained at 6-month follow-up among participants in the CBT Bytesize group. 5. CYP receiving CBT Bytesize will demonstrate improvement on routine outcome measures (ROMs) such as the RCADS, YP-CORE, and GBOs from baseline to post-intervention. 6. Compared to the TAU group, the CBT Bytesize group will show greater gains in specific domains such as engagement, session completion, and goal attainment. |
| Ethics approval(s) |
Approved 20/12/2021, Manchester Metropolitan University REC (Ormond Building, Lower Ormond Street, Manchester, M15 6BX, United Kingdom; +44 (0)161 247 2222; press@mmu.ac.uk), ref: 34434 |
| Health condition(s) or problem(s) studied | Anxiety disorders in children and young people |
| Intervention | Current interventions as of 08/07/2025: The intervention group consisted of children and young people who voluntarily opted into the CBT Bitesize programme following identification from Healios’ existing waiting list to access mental health support. Clinicians screened potential participants against the inclusion/exclusion criteria. Those deemed eligible were contacted via telephone by Healios clinicians and offered the option to either remain on the waiting list or begin the CBT Bitesize programme. Comprehensive information about the intervention was also sent to families via email, and only participants who gave informed consent to participate were enrolled. A matched control group was retrospectively assembled from Healios clinical records, comprising young people who had previously received treatment-as-usual (TAU) online CBT during a comparable period. Participants in the control group were matched to those in the intervention group based on key demographic and clinical characteristics, including age, gender, type and severity of presenting difficulties. If more than one match existed for a CBT Bitesize client, one match was randomly selected. The matched young person was then removed from the sample of clients engaging with TAU to ensure that the same young person could not be a match for multiple CBT Bitesize participants. This matching procedure aimed to enhance group comparability and reduce potential confounding, acknowledging the limitations inherent in non-randomised study designs. In addition to quantitative outcome measures collected via self-report at baseline, post-treatment, and follow-up time points, the study incorporated a qualitative component to explore participants' and clinicians’ experiences of the intervention. Semi-structured interviews were conducted with young people following completion of the programme, and focus groups were held with participating clinicians. These qualitative data were analysed thematically to provide in-depth insights into the feasibility, usability, and perceived value of the CBT Bitesize intervention. This mixed-methods approach was selected to enable a comprehensive evaluation of a novel, digitally delivered CBT programme within a real-world service context, addressing both measurable outcomes and experiential factors relevant to its future scalability and implementation. _____ Previous interventions: Participants were randomised using a computer-generated random number sequence with block randomisation to ensure equal allocation. The intervention under evaluation is CBT Bytesize, a brief, hybrid-format cognitive-behavioural therapy (CBT) programme designed for children and young people (CYP) experiencing anxiety. It combines digital self-help content delivered through an online platform with therapist-guided sessions, aiming to improve accessibility, engagement, and therapeutic outcomes in routine clinical settings. CBT Bytesize includes: 1. Structured, brief CBT modules aligned with core CBT principles (e.g., psychoeducation, cognitive restructuring, behavioural experiments). 2. Interactive digital content, such as videos, exercises, and reflective tasks, tailored to a younger audience. 3. Therapist support, provided either face-to-face or via telehealth, to reinforce learning, personalise content, and maintain therapeutic engagement. 4. Typically delivered over 6–8 sessions, the programme is designed to be time-efficient while still therapeutically effective. The comparator is a matched historical control group that received treatment-as-usual (TAU) online CBT, representing standard care previously delivered by the service. TAU included more traditional CBT protocols without the streamlined, digital–hybrid enhancements of the CBT Bytesize model. |
| Intervention type | Mixed |
| Primary outcome measure | Current primary outcome measure as of 08/07/2025: 1. Symptoms of various anxiety disorders and low mood, measured using the Revised Child Anxiety and Depression Scale (RCADS) at baseline (T1), mid-intervention (T2) and post-intervention (T3). _____ Previous primary outcome measure: Symptoms of various anxiety disorders and low mood, measured using the Revised Child Anxiety and Depression Scale (RCADS) at baseline, post-intervention, and 6-month follow-up |
| Secondary outcome measures | Current secondary outcome measures as of 08/07/2025: 1. Psychological distress and functioning measured using the Young Person’s CORE (YP-CORE) at baseline (T1), mid-intervention (T2) and post-intervention (T3). 2. Feasibility, assessed through session attendance and completion rates over the intervention period. 3. Acceptability, evaluated post-intervention using qualitative interviews and satisfaction surveys with participants (young people) and therapists. _____ Previous secondary outcome measures: 1. Psychological distress and functioning measured using the Young Person’s CORE (YP-CORE) at baseline, post-intervention, and 6-month follow-up 2. Progress toward self-identified goals measured using the Goal-Based Outcomes (GBOs) at baseline, post-intervention, and 6-month follow-up 3. Feasibility assessed through session attendance and completion rates over the intervention period 4. Acceptability evaluated using qualitative interviews and satisfaction surveys with participants and therapists post-intervention |
| Overall study start date | 20/12/2021 |
| Completion date | 01/08/2023 |
Eligibility
| Participant type(s) | Patient, Service user |
|---|---|
| Age group | Child |
| Lower age limit | 11 Years |
| Upper age limit | 17 Years |
| Sex | Both |
| Target number of participants | Approximately 50 children and young people (CYP) to be recruited into the CBT Bytesize intervention arm. Approximately 4-6 clinicians to take part in the focus group, and around 10 interviews to be conducted with CYP who have taken part in Bytesize. |
| Total final enrolment | 192 |
| Key inclusion criteria | Current inclusion criteria as of 08/07/2025: 1. Being referred to Healios by contracted NHS trusts supporting young people in the UK 2. Having anxiety symptoms/anxiety disorder(s) and low mood as the primary presentation(s). Young people with comorbidities were not excluded, as long as the primary presentation was ‘anxiety’. 3. Access to a smartphone and the Internet 4. Good level of conversational English 5. Aged 11 to 17 years 6. Willing to talk about their experiences and provide feedback on the CBT Bitesize programme _____ Previous inclusion criteria: 1. Children and young people (CYP) aged 8 to 17 years 2. Referred to a CAMHS (Child and Adolescent Mental Health Services) team for anxiety-related difficulties 3. Deemed clinically appropriate for brief cognitive-behavioural therapy (CBT) by their care team 4. Able to understand and communicate in English, sufficient to engage with the intervention and complete outcome measures 5. Have access to a device (e.g., smartphone, tablet, or computer) and the internet to engage with the digital content 6. Provided informed consent/assent (with parental/guardian consent as appropriate based on age and service policy) |
| Key exclusion criteria | Current exclusion criteria as of 08/07/2025: 1. Presence of sight/hearing problems 2. Suicide attempts within the last three months and/or actively suicidal 3. Current safeguarding concerns, safeguarding investigations or criminal investigations 4. Not able/willing to provide assent to take part in CBT Bytesize, or parents/legal guardians not providing consent to take part in the programme. _____ Previous exclusion criteria: 1. Primary presenting difficulties that are not anxiety-related (e.g., severe depression, eating disorders, trauma, or psychosis) and are not suitable for brief CBT. 2. Level of clinical complexity or risk (e.g., high self-harm or safeguarding concerns) that would require more intensive or specialist interventions. 3. Insufficient English proficiency to understand intervention content or complete outcome measures. 4. Significant cognitive impairments or learning difficulties that would prevent engagement with the app-based or self-guided content. 5. Lack of access to a digital device or the internet, preventing full participation in the hybrid model of care. |
| Date of first enrolment | 21/12/2021 |
| Date of final enrolment | 01/02/2023 |
Locations
Countries of recruitment
- England
- Scotland
- United Kingdom
- Wales
Study participating centre
Grosvenor Square
Manchester
M15 6BH
United Kingdom
Sponsor information
University/education
Ormond Building
Lower Ormond Street
Manchester
M15 6BX
England
United Kingdom
| Phone | +44 (0)161 247 2000 |
|---|---|
| enquiries@mmu.ac.uk | |
| Website | https://www.mmu.ac.uk |
"ROR" |
https://ror.org/02hstj355 |
Industry
Vintage House
36-37 Albert Embankment
London
SE1 7TL
England
United Kingdom
| Phone | +44 (0)330 124 4222 |
|---|---|
| support@healios.org.uk | |
| Website | https://healios.org.uk/ |
Funders
Funder type
University/education
Private sector organisation / Universities (academic only)
- Alternative name(s)
- MMU
- Location
- United Kingdom
No information available
Results and Publications
| Intention to publish date | 15/09/2025 |
|---|---|
| Individual participant data (IPD) Intention to share | No |
| IPD sharing plan summary | Not expected to be made available |
| Publication and dissemination plan | Findings from this service evaluation will be disseminated through a range of academic, clinical, and public-facing channels to ensure that the results are accessible and impactful for diverse audiences. 1. Academic Dissemination: The results will be submitted for publication in a peer-reviewed journal focused on child and adolescent mental health, digital interventions, or clinical psychology (e.g., Child and Adolescent Mental Health, JMIR Mental Health, or Behaviour Research and Therapy). Abstracts will also be submitted to relevant academic conferences, such as the BABCP Annual Conference, the Association for Child and Adolescent Mental Health (ACAMH), and the International Society for Research in Child and Adolescent Psychopathology (ISRCAP). 2. Clinical and Service Dissemination: Summary reports and presentations will be shared with participating NHS services and local CAMHS teams to inform future service planning and implementation. Findings will also be submitted to NHS England's innovation or service improvement forums, where applicable. 3. Public and Participant-Focused Dissemination: A plain English summary of the results will be made available to participating families, clinicians, and young people through service websites or newsletters. We also plan to create short visual summaries or infographics suitable for digital sharing and potential use by third-sector partners or youth mental health advocacy groups. 4. Internal Stakeholder Engagement: Findings will be shared with commissioners and digital health developers involved in the design and deployment of CBT Bytesize to guide future adaptations and scalability. |
| IPD sharing plan | The dataset generated during the current study is not expected to be made available due to the need to protect children and young people's data on sensitive topics such as their mental health. The ethical approval received for this study covers data storage and handling for the purposes of the study, but the participants and their caregivers have not given their informed consent for their personal data to be publicly shared. |
Editorial Notes
08/07/2025: The following changes were made to the trial record:
1. The public title was changed from "CBT Bytesize: testing a new digital mental health tool for young people" to "Evaluating CBT Bytesize: a mixed-methods feasibility trial of a blended digital CBT intervention for adolescent anxiety and low mood".
2. The scientific title was changed from "CBT Bytesize: a feasibility randomised controlled trial of a novel CBT-based digital mental health intervention for young people" to "Evaluating CBT Bytesize: a mixed-methods feasibility trial of a blended digital CBT intervention for adolescent anxiety and low mood".
3. The study objectives were changed.
4. The study design was changed from "Single-centre feasibility randomized controlled trial utilising a fixed-methods design" to "Matched mixed-methods feasibility and usability trial".
5. The interventions were changed.
6. The primary outcome measure was changed.
7. The secondary outcome measures were changed.
8. The inclusion criteria were changed.
9. The exclusion criteria were changed.
10. The plain English summary was updated to reflect these changes.
29/05/2025: Study's existence confirmed by the Manchester Metropolitan University REC.
