A new way of delivering therapist-led online cognitive behavioural therapy (CBT) can reduce symptoms of depression and improve function, according to new University of Bristol-led research published in The Lancet Primary Care .
Depression affects millions of people and can have a major impact on daily life, relationships and work. Although CBT is an effective treatment, many people face barriers to accessing it, including long waiting lists and difficulties attending in-person appointments due to work commitments, caring responsibilities, living in more remote areas, or social anxiety.
Delivering CBT online using instant messaging is known to be effective, but therapy delivered by instant messaging alone does not support the practice of CBT outside the therapy session. The research aimed to find out whether integrating interactive online materials might improve engagement with therapy and increase access.
The INTERACT (Integrated therapist and online Cognitive Behavioural Therapy for depression in primary care) study tested a new form of therapy called ‘integrated CBT’. It combined one-to-one CBT delivered by instant messaging with an accredited CBT therapist, with worksheets and information that could be accessed, both during and between sessions, through a secure digital platform.
The National Institute for Health and Care Research (NIHR)-funded trial involved 451 adults with depression recruited from 67 GP practices across England. Half were offered integrated CBT using the online therapy platform in addition to their usual care, while the other half continued to receive usual care from their GP.
Integrated CBT consisted of nine to twelve therapist-led sessions tailored to each person's needs. Therapists worked with patients using written conversations in real time through the online platform and shared resources for patients to use during and between sessions to help them develop skills in managing negative thoughts and changing unhelpful behaviours.
After six months, people who received integrated CBT reported significantly fewer symptoms of depression than those receiving usual care alone. Those in the intervention group had a depression score that was, on average, 4.4 points lower than those in the usual care group. This difference was likely to be clinically important. The benefits were seen across a large and diverse group of patients recruited from routine primary care settings. Improvements were maintained over 12 months.
The findings suggest that this novel approach to delivering therapist-led online CBT could help increase access to evidence-based treatment for depression, particularly for people who cannot easily attend traditional in-person appointments. It may also help services offer more flexible ways of delivering mental health support.
Debbie Tallon , INTERACT Programme Manager and Senior Clinical Trials Manager at Bristol Medical School and lead author, said: "Depression is common, but many people face practical barriers to accessing psychological therapies. Our findings show that therapist-led CBT delivered using an online therapy platform which provides access to resources for patients to use within and between sessions can be an effective treatment option, giving people greater flexibility in how they receive care while maintaining the benefits of working with a qualified therapist."
Nicola Wiles, Professor of Epidemiology at the Centre for Academic Mental Health and Centre for Academic Primary Care at the University of Bristol, and senior author, said: "CBT is an effective treatment for depression, but demand for psychological therapies continues to outstrip capacity. Our study shows that integrating therapist support with online CBT materials can achieve meaningful improvements in depression symptoms and could become an important part of how NHS services meet growing need."
Professor Olivia Wu, NIHR Programme Director of Programme Grants for Applied Research (PGfAR), said: "These findings highlight how integrated, therapist-led digital CBT can deliver clinically meaningful and sustained improvements for people living with depression, offering an evidence-based option for those who struggle to access care in person. As the NHS looks to expand community-based, digital-first services, this trial shows what interventions like this can achieve for patients."
The INTERACT study was an eight-year programme of research led by the University of Bristol in collaboration with the Universities of Glasgow, York, Hull York Medical School, University College Dublin, and University College London.
Paper : Integrated therapist and online cognitive behavioural therapy in addition to usual care versus usual care for depression in primary care in England (INTERACT): a two-group, parallel, multicentre, randomised controlled trial . Published in The Lancet Primary Care . June 2026.
Infographic: Downloadable version available from the INTERACT study website .
Further information
The Integrated Therapist and Online CBT for Depression in primary care (INTERACT) trial was funded by an NIHR Programme Grants for Applied Research award (RP-PG-0514–20012). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. This trial was also supported by the NIHR Bristol Biomedical Research Centre. Supplementary funding was provided by the NIHR School for Primary Care Research (SPCR–2014-10043 Award: L).
About the Centre for Academic Mental Health
The Centre for Academic Mental Health (CAMH) at the University of Bristol is part of Population Health Sciences (PHS), an internationally recognised centre for research excellence and teaching within Bristol Medical School.
CAMH conducts high quality research and teaching on mental health within the Medical School, the wider University and externally.
About the Centre for Academic Primary Care
The Centre for Academic Primary Care (CAPC) at the University of Bristol is a leading centre for primary care research in the UK, one of ten forming the NIHR School for Primary Care Research . It sits within Bristol Medical School, an internationally recognised centre of excellence for population health research and teaching.
We work with patients and the public to make sure our research in primary care focuses on what really matters to people and communities.
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About the National Institute for Health and Care Research
The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research.
We do this by:
funding high quality, timely research that benefits the NHS, public health and social care
investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services
partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research
attracting, training and supporting the best researchers to tackle complex health and social care challenges
collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system
funding applied global health research and training to meet the needs of the poorest people in low and middle income countries
NIHR is funded by the Department of Health and Social Care. Our work in low and middle income countries is principally funded through UK international development funding from the UK government.
The Lancet
Integrated therapist and online cognitive behavioural therapy in addition to usual care versus usual care for depression in primary care in England (INTERACT): a two-group, parallel, multicentre, randomised controlled trial
19-Jun-2026