Cobra Behavioural Activation Trial

COBRA Trial (Cost and Outcome of Behavioural Activation versus Cognitive Behaviour Therapy for Depression)


The trial and its aims

Clinical depression is a common and debilitating mental health disorder, being the second largest cause of global disability. The impact on economic output across the world is projected to be US$5.36 trillion between 2011 and 2030.

Cognitive Behavioural Therapy (CBT) is recommended as a treatment for depression by the UK National Institute for Health and Care Excellence (NICE). However, it is a complex treatment delivered by highly trained professionals who are expensive to employ, and this limits access to CBT. Behavioural Activation (BA) is also an effective treatment for depression and is relatively simple, meaning it can be delivered by junior staff with less training, making it a cost-effective option.

NICE recommended research to directly compare the outcomes and costs of BA with CBT. COBRA was a multi-centre randomised controlled trial funded by the UK National Institute for Health Research (NIHR) Health Technology Assessment Programme, led by Professor David Richards, NIHR Senior Investigator and head of the Complex Interventions Research Group.


What are Behavioural Activation and Cognitive Behavioural Therapy?

BA is based on the idea that certain behaviours such as inactivity are key factors in depression. The therapist encourages patients to focus on meaningful activities driven by their own personal values as a way of overcoming depression.

CBT is based on the idea that certain ways of thinking can maintain depression. The therapist helps patients to identify any unhelpful thoughts that may make them feel depressed. CBT aims to change those ways of thinking and help people think in more realistic and helpful ways.


Who was involved?

Participants who met diagnostic criteria for major depressive disorder were recruited through primary care and psychological therapy services in Devon, Durham and Leeds. The 440 participants were split into two groups – 219 were given CBT and 221 were given BA. The participants were followed up and assessed at six, 12 and 18 months.

BA was delivered by National Health Service (NHS) junior mental health workers and CBT was delivered by NHS professional or equivalently qualified psychotherapists. All therapists were given a 5 day training course in BA or CBT, delivered by trial team experts. 


The findings

A year after the start of treatment, BA was found to be non-inferior to (not worse than) CBT, with around two-thirds of people in both groups reporting at least a 50% reduction in depressive symptoms. Participants in both groups also reported similar numbers of depression-free days and anxiety diagnoses, and were equally likely to experience remission. BA was found to be around 20% cheaper to deliver than CBT.

The COBRA trial demonstrated that junior mental health workers with no professional training in psychological therapies can deliver BA, a simple psychological treatment, with no lesser effect than CBT and at less cost.


The published paper can be found free of charge online at or by clicking on this link: COBRA article Lancet 22 July 2016

Cost and Outcome of Behavioural Activation versus Cognitive Behaviour Therapy for Depression (COBRA): results of a non-inferiority randomised controlled trial’ published in The Lancet on Friday July 22. Authors are David A Richards, PhD; David Ekers, PhD; Dean McMillan, PhD; Rod S Taylor, PhD; Sarah Byford, PhD; Fiona C Warren, PhD; Barbara Barrett, PhD; Paul A Farrand, PhD; Simon Gilbody, DPhil; Willem Kuyken, PhD; Heather O'Mahen, PhD; Ed R Watkins, PhD; Kim A Wright, PhD; Steven D Hollon, PhD; Nigel Reed, BSc; Shelley Rhodes, PhD; Emily Fletcher, MSc; Katie Finning, BSc.