Condition category
Mental and Behavioural Disorders
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims
Depression causes misery to many people and is a major health problem in the UK. Although effective treatments are available, many people do not have access to them and we are always looking for treatments that are easier and quicker for patients to receive. New ways of organising treatment have been developed in the United States but we do not know if they are better than usual care in the UK. Therefore, this study will investigate a way of organising the way we deliver treatment for depression. This is called ‘collaborative care for depression’ and it is being compared with the usual care given by General Practitioners (GPs).

Who can participate?
We are asking people from a number of different GP surgeries in three UK areas if they would like to take part. All participants will have a diagnosis of depression.

What does the study involve?
If people agree to take part in the research the first thing we will want to do is to find out about them. We will need to ask about their current and past mental health as well as their life more generally. This meeting will take about 90 minutes. We then arrange to see people in 4, 12 and 36 months’ time. These meetings will be a little shorter as they only involve filling out some questionnaires. We expect these meetings to take about 45 minutes. We also need to collect some information from their medical records. The research study will last for five-and-a-half years, but individual participants will only be involved for 36 months.
Every participant will continue to have their treatment managed by their GP, but people from half of the GP surgeries will also receive Collaborative Care, while the other half will receive usual care (exactly the same treatment as if they chose not to take part in the study). The decision about whether a surgery will offer Collaborative Care is made totally by chance, and participants will not know which group their GP surgery is in until they decide to take part in the study. People receiving Collaborative Care are assigned a case manager, who is a health worker specially trained to help people with depression. Case managers help to organise the person’s care and will give them advice on overcoming depression. For example, the case manager may advise about medication or explain some very simple ways that a person can help themselves to start to feel better. Case managers see people face to face initially, at a time and place to suit them, and the meeting will usually take about 40 minutes. After this first meeting, they will telephone the person at regular times to support them in their treatment. These calls take about 15 minutes, and will be booked at times to suit the patient. Usually, the case manager will call once a week for the first month and then once a fortnight for the next 3 months, but how often they call is totally up to the patient. Participants have contact with the case manager for 4 months.

What are the possible benefits and risks of participating?
We hope that both the new treatment and usual care will help participants. The information we get from this study may help us to treat future patients with depression better. We are not aware of any side effects, disadvantages or risks to participants of taking part in this research.

Where is the study run from?
The University of Exeter (UK)

When is the study starting and how long is it expected to run for?
September 2008 to February 2014

Who is funding the study?
The UK Medical Research Council

Who is the main contact?
Professor David Richards

Trial website

Contact information



Primary contact

Prof David Richards


Contact details

University of Exeter Medical School
Haighton Building
University of Exeter
St Luke's Campus
Heavitree Road
United Kingdom
+44 (0)1392 724615

Additional identifiers

EudraCT number number

Protocol/serial number

MRC ref: G0701013

Study information

Scientific title

Multi-centre randomised controlled trial of collaborative care for depression


CADET (CollAborative DEpression Trial)

Study hypothesis

Is collaborative care more clinically and cost effective than usual care in the management of moderate to severe depression in UK primary care?

More details can be found at

Ethics approval

The study has received Multi-Centre Research Ethics Committee approval from the South West Research Ethics Committee. Local Research Ethics Committee and NHS Research and Development approvals have also been given for each recruitment site.

Study design

Multicentre two-arm cluster-randomised controlled trial

Primary study design


Secondary study design

Cluster randomised trial

Trial setting

GP practices

Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet




Intervention group:
UK-specific collaborative care protocol developed from our Trial Platform delivered via scheduled telephone and face-to-face contacts by a supervised case manager over four months and including:
1. A multi-professional approach to patient care
2. A structured patient management plan including medication support and/or cognitive behavioural therapy (CBT) based behavioural activation
3. Scheduled patient follow-ups
4. Enhanced inter-professional communication

The control group will receive usual care from their GP.

Intervention is for 4 months, follow-ups are at the end of intervention (4 months from recruitment) and 12 months from recruitment.

Intervention type



Not Specified

Drug names

Primary outcome measure

Self-report severity of depression at 4 and 12 months follow-up, assessed using the Patient Health Questionnaire-9 (PHQ9). The PHQ9 is a self-report measure and therefore less subject to observer bias. It is sensitive to change with good psychometric properties and we have recently validated its sensitivity and specificity for a UK population.

Secondary outcome measures

The following outcome measures except CSQ-8 will be taken at baseline, 4 and 12 months follow-up:
1. Diagnosis of depression assessed by Clinical Interview Schedule (CIS-R), a computerised interview, and the Beck Depression Inventory II (BDI-II)
2. Health related quality of life, assessed by the SF-36 Health Survey
3. Health care utilisation, measured using case records and a patient service utilisation questionnaire
4. Health state utilities, assessed by EuroQoL
5. Satisfaction with care, measured by the Client Satisfaction Questionnaire (CSQ-8) at 4 months
6. Economic analysis. The incremental cost per Quality-Adjusted Life Years (QALY) of the intervention compared to the control will be calculated from NHS and Personal Social Services (PSS) perspectives.

Process data will be collected within the trial. The extensive quantitative and qualitative work in our pilot trial has indicated that the planned intervention is effective and acceptable, and our process evaluation in the main trial will focus on:
1. The process of implementation of the intervention, and
2. Mechanisms of change and differential response in patient subgroups

Investigation of the process of implementation will involve qualitative interviews with patients, GPs, case managers and specialist professionals, augmented with routinely collected data on from case records and session audio-tapes. Key stakeholders including GPs, patients, case managers and supervisors will be purposively sampled to represent a range and diversity of views and experiences. We will conduct between 30 - 40 interviews with these stakeholders until theoretical saturation has been achieved. All interviews will be audio-taped and transcribed verbatim. The analysis will examine the implementation of collaborative care, with a focus on differences between sites and different case managers. Investigation of mechanisms of change and differential response in patient subgroups will include quantitative measurement of key patient baseline characteristics (e.g. severity, duration of depression, patient preferences, attitudes towards treatment), treatment process measures (e.g. therapeutic alliance), contextual practice variables (e.g. Quality and Outcome Framework compliance rates, anti-depressant prescription rates; availability of counselling and other mental health services) and will follow conventional procedures for analysis.

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

We will include patients (both males and females) meeting the diagnostic criteria for depression who are aged 18 years and above and who are not currently receiving treatment for depression from specialist mental health services. We will establish the diagnosis of depression by the use of the Clinical Interview Schedule (CIS-R) undertaken by a research worker. We wish our trial to reflect the real world as closely as possible by including all patients with depression; we will therefore include both patients newly identified as depressed, with or without one or more previous depressive episodes, and those with a current depressive illness which has not responded to primary care management in the previous four months. We will also include patients who are suffering from peri- or post-natal depression, with either co-morbid physical illness or co-morbid non-psychotic functional disorders, such as anxiety. In line with the pragmatic nature of this trial, we will reflect usual GP care and participants will be eligible to participate whether they are in receipt of antidepressant medication or not.

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Patients whose risk of suicide is sufficiently acute to demand immediate management by a crisis team. Case managers will be trained to recognise and manage less acute risk through applying the procedures taught in the STORM (Skills-based Training On Risk Management) training, we will follow the trial suicide protocol. We will ensure that the patient's GP is involved immediately so they can take appropriate action for patients with suicidal plans.
2. Psychotic patients
3. Patients where the low mood is better explained by a simple bereavement reaction
4. Patients whose primary presenting problem is alcohol or drug abuse

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

University of Exeter Medical School
United Kingdom

Sponsor information


University of Exeter (UK)

Sponsor details

Northcote House
The Queen's Drive
United Kingdom
+44 (0)1392 661000

Sponsor type




Funder type


Funder name

Medical Research Council (UK) (ref: G0701013)

Alternative name(s)


Funding Body Type

government organisation

Funding Body Subtype

National government


United Kingdom

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)

Publication list

2009 protocol in:
2013 results in:
2014 results in:
2016 results in:

Publication citations

  1. Protocol

    Richards DA, Hughes-Morley A, Hayes RA, Araya R, Barkham M, Bland JM, Bower P, Cape J, Chew-Graham CA, Gask L, Gilbody S, Green C, Kessler D, Lewis G, Lovell K, Manning C, Pilling S, Collaborative Depression Trial (CADET): multi-centre randomised controlled trial of collaborative care for depression--study protocol., BMC Health Serv Res, 2009, 9, 188, doi: 10.1186/1472-6963-9-188.

  2. Results

    Richards DA, Hill JJ, Gask L, Lovell K, Chew-Graham C, Bower P, Cape J, Pilling S, Araya R, Kessler D, Bland JM, Green C, Gilbody S, Lewis G, Manning C, Hughes-Morley A, Barkham M, Clinical effectiveness of collaborative care for depression in UK primary care (CADET): cluster randomised controlled trial., BMJ, 2013, 347, f4913.

  3. Results

    Coupe N, Anderson E, Gask L, Sykes P, Richards DA, Chew-Graham C, Facilitating professional liaison in collaborative care for depression in UK primary care; a qualitative study utilising normalisation process theory, BMC Fam Pract, 2014, doi: 10.1186/1471-2296-15-78.

  4. Results

    Richards DA, Bower P, Chew-Graham C, Gask L, Lovell K, Cape J, Pilling S, Araya R, Kessler D, Barkham M, Bland JM, Gilbody S, Green C, Lewis G, Manning C, Kontopantelis E, Hill JJ, Hughes-Morley A, Russell A, Clinical effectiveness and cost-effectiveness of collaborative care for depression in UK primary care (CADET): a cluster randomised controlled trial, Health Technol Assess, 2016, 20, 14), 1-192, doi: 10.3310/hta20140.

Additional files

Editorial Notes

26/02/2016: Publication reference added. On 09/04/2014 the overall trial end date was changed from 31/08/2012 to 28/02/2014. On 17/01/2012 the following changes were made to the trial record: 1. The overall trial start date was changed from 01/06/2009 to 01/09/2008. 2. The overall trial end date was changed from 28/02/2012 to 31/08/2012.