Plain English Summary
Background and study aims
Many patients with depression who are prescribed antidepressants by their GP do not get better after 6 weeks of treatment. Currently there is little evidence about what alternative treatment options doctors should discuss with patients at this time. Cognitive behavioural therapy (CBT) is a type of talking therapy that has been shown to help patients with mild to moderate depression but there is little evidence about its effectiveness in patients who have not initially responded to antidepressants. In this study, we will examine whether patients who have not got better on antidepressants and go on to receive CBT as well as their medication are more likely to get better than patients who just continue to take their antidepressants over 12 months. We will also look at how much this treatment costs and patients' views and experiences of it.
Who can participate?
Patients aged 18-75 with depression who have been taking antidepressants for at least 6 weeks.
What does the study involve?
Patients will be invited to participate by their GP (in person or by letter) and those who are interested will be invited to meet with a researcher to discuss their participation in the study. All patients will be asked to sign a consent form to confirm that they fully understand what the study will involve. If you are eligible and willing to take part in the research, you will then be randomly allocated to one of two treatment groups, either: (1) CBT in addition to usual care, which includes antidepressants; or (2) usual care, including antidepressants. If you are included in Group 1, you will be invited to attend CBT sessions. Each session will last 50 minutes. Sessions will initially take place once a week but later on you and your therapist may decide that these sessions will occur less frequently. You would receive 12-18 sessions of CBT over about 6 months. If you are included in Group 2, you will continue to be under the normal care of your GP for the management of your depression. There will be no restrictions on the treatments that you can receive. Participants will be asked to complete a questionnaire at this time and again after 3, 6, 9 and 12 months. By comparing the two groups, we will be able to determine whether CBT is an effective treatment for this patient group. Participants will also be asked for their permission for the research team to have access to your medical records held at your GPs surgery and to any hospital records. You would also be asked to give your consent for any CBT treatment sessions to be recorded using a digital voice recorder.
What are the possible benefits and risks of participating?
We hope that the treatment will help those who take part. However, this cannot be guaranteed. The results of the study will help doctors in the future to decide on the best treatment for someone who is depressed. Some of the questions that you will be asked during the assessment are personal and sometimes people can find it upsetting to discuss these issues. However, you don't have to answer anything you don't want to. The researcher will be able to offer support during the appointment if you are upset, but would also contact the doctors or care workers who normally provide care for you, if further support is necessary.
Where is the study run from?
University of Bristol (UK).
When is the study starting and how long is it expected to run for?
The study started in May 2008 and will run until March 2015.
Who is funding the study?
NIHR Health Technology Assessment Programme - HTA (UK).
Who is the main contact?
Dr Nicola Wiles
Dr Nicola Wiles
Centre for Academic Mental Health
School of Social and Community Medicine
University of Bristol
+44 (0)117 331 3358
Cognitive Behavioural Therapy as an adjunct to pharmacotherapy for treatment resistant depression in primary care: a randomised controlled trial
To determine the clinical and cost-effectiveness of Cognitive Behavioural Therapy (CBT) in addition to pharmacotherapy in reducing depressive symptoms and improving quality of life over the following 12 months (compared to pharmacotherapy plus usual care) in patients with Treatment Resistant Depression (TRD)
In addition, a qualitative study will be conducted to:
1. Explore patient's views and experiences of CBT
2. Identify patient's reasons for completing or not completing therapy
3. To describe 'usual care' for this patient group
More details can be found at: http://www.nets.nihr.ac.uk/projects/hta/0640402
Protocol can be found at: http://www.nets.nihr.ac.uk/__data/assets/pdf_file/0019/51418/PRO-06-404-02.pdf
In addition, to determine whether the intervention is effective in reducing depressive symptoms and improving quality of life over the long-term (approximately 4 years post-randomisation), compared with usual care alone, and whether this strategy is cost-effective
A nested qualitative study will also be conducted with those who completed the long-term follow-up study questionnaire in order to explore how patients from both arms of the trial continued to manage their depression over the long-term (since the 12-month follow-up). Amongst those who received CBT during the trial, the study will also explore the extent to which they have continued to use the techniques learnt and to incorporate CBT strategies into their lives.
West Midlands Research Ethics Committee, 26/02/2008, ref: 07/H1208/60
Multi-centre randomised controlled trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Patient information can be found at: http://www.thecobaltstudy.ac.uk/docs/pt-info.pdf
Patients will be randomised to one of two groups. All patients will be taking antidepressants at the point of randomisation. Both groups will continue their antidepressants as directed by their GP.
In Group 1 (intervention group), subjects will be randomised to receive CBT in addition to usual care (including pharmacotherapy). Each patient will receive a course of 12-18 sessions of CBT.
In Group 2 (control group), subjects would continue to receive their usual care from their GP (including antidepressants).
Primary outcome measure
BDI score at 6-months post-randomisation, specifically a binary variable representing response, defined as a reduction in depressive symptoms of at least 50% compared to baseline.
Secondary outcome measures
Current secondary outcome measures as of 19/02/2013:
Remission of symptoms, quality of life and use of antidepressants at 6 months post-randomisation, together with outcomes measured at 12 months post-randomisation and long-term outcomes measured approximately 4 years post-randomisation.
Previous secondary outcome measures until 19/02/2013:
Remission of symptoms, quality of life and use of antidepressants at 6 months post-randomisation, together with outcomes measured at 12 months post-randomisation.
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Aged 18-75 years
2. Patients currently taking antidepressant medication and who have done so for at least 6 weeks at an adequate dose
3. Patients who score 14 or more on the Beck Depression Inventory (BDI)
4. Have adhered to their medication
5. Meet the World Health Organization International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) criteria for depression
Target number of participants
Participant exclusion criteria
1. Bipolar disorder
2. Psychosis or alcohol/substance abuse/dependence
3. Not able to complete the study questionnaires
4. Currently receiving CBT or other psychotherapy or secondary care for depression
5. Have received CBT in the past 3 years
6. Patients who would not be able to benefit from talking therapy without an interpreter
7. Women who are pregnant at time of recruitment will be excluded from the trial but women who become pregnant during the trial may continue, providing they have approval and permission to do so from their GP
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Centre for Academic Mental Health
University of Bristol (UK)
c/o Dr Birgit Whitman
Research Governance and Compliance Manager
University of Bristol
Research and Enterprise Development
+44 (0)117 331 7130
Health Technology Assessment Programme
NIHR Health Technology Assessment Programme, HTA
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Not provided at time of registration
Intention to publish date
Participant level data
Not provided at time of registration
Basic results (scientific)
2012 protocol in: http://www.ncbi.nlm.nih.gov/pubmed/22101205
2012 patients' reasons for declining contact in: http://www.ncbi.nlm.nih.gov/pubmed/22546597
2013 results in: http://www.ncbi.nlm.nih.gov/pubmed/23219570
2013 patients' experiences in: http://www.ncbi.nlm.nih.gov/pubmed/23851972
2013 depressed clients' experiences in: http://www.ncbi.nlm.nih.gov/pubmed/24117909
2013 comparison of four different approaches to measuring health utility in: http://www.ncbi.nlm.nih.gov/pubmed/23659557
2014 results in: http://www.ncbi.nlm.nih.gov/pubmed/24824481
2014 economic evaluation results in: http://www.ncbi.nlm.nih.gov/pubmed/24262818
2014 adherence to and divergence from trial criteria results in: http://www.ncbi.nlm.nih.gov/pubmed/24621557
2016 follow-up results in: http://www.ncbi.nlm.nih.gov/pubmed/26777773
Thomas LJ, Abel A, Ridgway N, Peters T, Kessler D, Hollinghurst S, Turner K, Garland A, Jerrom B, Morrison J, Williams C, Campbell J, Kuyken W, Lewis G, Wiles N, Cognitive behavioural therapy as an adjunct to pharmacotherapy for treatment resistant depression in primary care: the CoBalT randomised controlled trial protocol., Contemp Clin Trials, 2012, 33, 2, 312-319, doi: 10.1016/j.cct.2011.10.016.
Wiles N, Thomas L, Abel A, Ridgway N, Turner N, Campbell J, Garland A, Hollinghurst S, Jerrom B, Kessler D, Kuyken W, Morrison J, Turner K, Williams C, Peters T, Lewis G, Cognitive behavioural therapy as an adjunct to pharmacotherapy for primary care based patients with treatment resistant depression: results of the CoBalT randomised controlled trial., Lancet, 2013, 381, 9864, 375-384, doi: 10.1016/S0140-6736(12)61552-9.
Comparison of four different approaches to measuring health utility
Turner N, Campbell J, Peters TJ, Wiles N, Hollinghurst S, A comparison of four different approaches to measuring health utility in depressed patients., Health Qual Life Outcomes, 2013, 11, 81, doi: 10.1186/1477-7525-11-81.
Wiles N, Thomas L, Abel A, Barnes M, Carroll F, Ridgway N, Sherlock S, Turner N, Button K, Odondi L, Metcalfe C, Owen-Smith A, Campbell J, Garland A, Hollinghurst S, Jerrom B, Kessler D, Kuyken W, Morrison J, Turner K, Williams C, Peters T, Lewis G, Clinical effectiveness and cost-effectiveness of cognitive behavioural therapy as an adjunct to pharmacotherapy for treatment-resistant depression in primary care: the CoBalT randomised controlled trial., Health Technol Assess, 2014, 18, 31, 1-167, vii-viii, doi: 10.3310/hta18310.
Economic evaluation results
Hollinghurst S, Carroll FE, Abel A, Campbell J, Garland A, Jerrom B, Kessler D, Kuyken W, Morrison J, Ridgway N, Thomas L, Turner K, Williams C, Peters TJ, Lewis G, Wiles N, Cost-effectiveness of cognitive-behavioural therapy as an adjunct to pharmacotherapy for treatment-resistant depression in primary care: economic evaluation of the CoBalT Trial., Br J Psychiatry, 2014, 204, 1, 69-76, doi: 10.1192/bjp.bp.112.125286.
Adherence to and divergence from trial criteria results
Jenkinson CE, Winder RE, Sugg HV, Roberts MJ, Ridgway N, Kuyken W, Wiles N, Kessler D, Campbell J, Why do GPs exclude patients from participating in research? An exploration of adherence to and divergence from trial criteria., Fam Pract, 2014, 31, 3, 364-370, doi: 10.1093/fampra/cmu005.
Barnes M, Wiles N, Morrison J, Kessler D, Williams C, Kuyken W, Lewis G, Turner K, Exploring patients' reasons for declining contact in a cognitive behavioural therapy randomised controlled trial in primary care., Br J Gen Pract, 2012, 62, 598, e371-7, doi: 10.3399/bjgp12X641492.
Simmonds B, Turner N, Thomas L, Campbell J, Lewis G, Wiles N, Turner K, Patients' experiences of participating in a large-scale trial of cognitive behavioural therapy for depression: a mixed methods study., Fam Pract, 2013, 30, 6, 705-711, doi: 10.1093/fampra/cmt028.
Barnes M, Sherlock S, Thomas L, Kessler D, Kuyken W, Owen-Smith A, Lewis G, Wiles N, Turner K, No pain, no gain: depressed clients' experiences of cognitive behavioural therapy., Br J Clin Psychol, 2013, 52, 4, 347-364, doi: 10.1111/bjc.12021.
Wiles NJ, Thomas L, Turner N, Garfield K, Kounali D, Campbell J, Kessler D, Kuyken W, Lewis G, Morrison J, Williams C, Peters TJ, Hollinghurst S, Long-term effectiveness and cost-effectiveness of cognitive behavioural therapy as an adjunct to pharmacotherapy for treatment-resistant depression in primary care: follow-up of the CoBalT randomised controlled trial, Lancet Psychiatry, 2016 , doi: 10.1016/S2215-0366(15)00495-2.