A Cognitive Behavioural Therapists Guide to Evidence

A cognitive behavioural therapist’s guide to evidence

Mental health problems are serious and widespread. We need therapies that work.

As a CBT therapist you will have been taught during training about some of the key research studies and learned that CBT is based on evidence from research and clinical practice. The science behind it is strong.

A key part of our mission is to help to share knowledge and understanding about CBT, so that more people experiencing mental health problems get the best care. As part of this, we want people to understand the science, so they can see why CBT could be helpful for them or their loved ones.

As a CBT therapist, part of your continuing learning and development should involve reading about and understanding the evidence for the therapeutic techniques you are using. Along with supervision, this can help guide your clinical practice. It will also help you to explain to clients what you are doing and why. You may also want to become involved in research yourself at some point.

CBT is an evidence-based therapy

CBT has a wide-ranging evidence base showing effectiveness for many different people and problems. It is widely recommended worldwide. A key feature of CBT is that is based on scientific evidence, and continues to develop this evidence. We are continually learning and developing treatments and approaches and checking that these are helpful and are delivered in ways that enable the people who need them to obtain the best possible outcomes. This commitment to evidence-base is reflected in BABCP’s core values, and has enabled the field of CBT to progress into many different areas with confidence.

Why is it important to know about the evidence base as a CBT therapist?

As a CBT therapist you will likely be familiar with the importance that cognitive behavioural therapies place on building a robust theoretical and experimental foundation for therapy, and on continuing to learn from new research in the field. Keeping up to date with the research evidence in your area has multiple benefits, including that:

  • You are able to know what is most effective to use in your practice, to help the clients you work with.
  • You can continue to learn and develop as a reflective practitioner.
  • You can share information with commissioners and referrers, helping them to understand more about CBT good practice to ensure the services available are following the evidence base (e.g. offering data on the number of sessions needed). This may be particularly helpful if you are a service lead or CBT champion, but may also be useful for individual clinicians in a service or for independent therapists.
  • You can share information about evidence with clients who come to see you, enabling them to make an informed choice about the type of therapy they receive. We have written a page with lay audiences in mind, which you can share with people who are coming to see you for therapy. You may also wish to share some of the additional resources on this page, depending on how much your client wants to read about the evidence behind CBT.
  • You can weigh up the strengths and weaknesses of different studies and use this to inform clients, service policy and individual practice. This involves understanding study quality.

What do we mean by evidence?

When we talk about the evidence base we are mostly referring to research studies which have been carried out and written up in academic journals which are peer-reviewed. This means that the quality of the articles has been assessed by other researchers working in similar fields.

Other important parts of the evidence-base include writing about the underlying theories behind CBT, information from clinical outcomes in CBT services, information from clinical guidelines, and patient views on different types of treatment. These different elements are summarised in the diagram below.

Figure 1. Elements of empirically grounded clinical interventions, P.Salkovskis

Different types of study

Some of the different types of design that you might come across are summarised below, along with some key terms you might come across when reading about evidence. Different types of study give us different types of evidence. There is also more about this in the chapter by Rakovshik linked to below.

Single Case Reports: these give a detailed report of the presenting problem, treatment, outcome and follow-up of a particular person accessing CBT.

Single Case Experimental Design: In this design, a variable of interest is experimentally manipulated in order to test a hypothesis about what will happen. These can be carried out with one participant. A key feature is repeated measurement at baseline and throughout.

Consecutive Single Case Series: These are like the single case experimental design but with more than one participant. 

Randomised Controlled Trial: These studies involve randomly assigning a number of similar people to a treatment (e.g. CBT), and randomly assigning the other people either a treatment as usual, no treatment (sometimes a placebo), or a different intervention. Outcomes are measured at specific times and statistical methods are used to assess difference. The groups are followed up to see how effective the experimental intervention is.

Placebo: a placebo is an inactive substance or treatment that looks like the drug or treatment being tested.

Dismantling study: this is a study which investigates therapies with multiple components, with the goal of understanding which aspects of treatment are the active mechanisms of change and how much they contribute to the overall effect of the therapy.

Research protocol: This is the guidebook for a research study, which describes what the research aims are and how they will be realised by the researchers. It usually goes through what will happen step-by-step and reports in detail how the research will be carried out and managed.

Generalisation: refers to the process of inferring that evidence from specific research trials is likely to translate to wider, more general settings. Sometimes additional studies are carried out with other populations to ensure generalisability can be inferred.

Research hypothesis: this is a specific, clear, testable proposition or predictive statement about what is predicted to happen as the outcome of a research study.

Quantitative research: research that is quantitative uses quantifiable (numerical) data and statistical techniques to investigate research hypotheses.

Qualitative research: research that is qualitative uses non-numerical data (e.g. observations, interviews) and tend to focus on interpreting meaning and prioritising individual experiences.

Effectiveness versus Efficacy: You may also come across the terms effectiveness and efficacy. Efficacy is the measurement of the performance of an intervention under ideal and controlled conditions. Effectiveness refers to an intervention’s performance under ‘real world’ conditions.

Research of all different types is important, and often putting information together from different types of research (triangulation) can be very helpful to get a richer picture of what is going on. The ‘hourglass model’ below shows how single case studies might lead up to full randomised controlled trials, and how in turn RCTs can lead to further studies to assess generalisability in different populations and further knowledge about the intervention and the mechanisms of change.

Salkovskis, P. M. (1995). Demonstrating specific effects in cognitive and behavioural therapy, in M. Aveline & D. Shapiro (Eds.), Research foundations for psychotherapy practice (pp. 191–228). Chichester, UK: Wiley.

Clinical Guidelines

Clinical guidelines are based on the findings of good quality research. It is important to be aware of the clinical guidelines in your field and for your geographical area, for example the NICE guidelines.

What are NICE guidelines?

The National Institute for Health and Care Excellence (CHECK), also known as NICE, regularly reviews the evidence for different problems and publishes guidelines on what they recommend. NICE Guidelines cover clinical care in England and Wales, and some guidelines also apply to N.Ireland. In Scotland the Scottish Matrix (2011) also sets out the available evidence base for psychological therapies for common mental health problems, and in Wales the Matrics Cymru has also been developed.

CBT is recommended in many of these guidelines and is a treatment provided by the NHS. If you want to read about the specific guidelines for a particular problem you are treating, you can go to www.nice.org.uk and search for the guidance summary for the problem.

Helpful sources of information for therapists as well as clients can be found at the following links.

Page on CBT evidence for potential clients


The Cochrane Database of Systematic Reviews is also a helpful resource. It is the leading journal and database for systematic reviews in healthcare.



For a helpful review of evidence for CBT try Chapter 10 in Layard, R., & Clark, D. M. (2015). Thrive. Princeton University Press.

Rakovshik, S. (2019). An Introduction to CBT Research. SAGE.

The authors and publisher have kindly given access to:

Chapter 4 Common Forms of Research in CBT

This book by Corrie and Lane is really useful and the authors and publisher have kindly given access to Chapter 1 Understanding Cognitive Behaviour Therapy

Corrie, S., & Lane, D. A. (2021). First Steps in Cognitive Behaviour Therapy. SAGE Publications Limited. Chapter 1


David, D., Cristea, I., & Hofmann, S. G. (2018). Why cognitive behavioural therapy is the current gold standard of psychotherapy. Frontiers in Psychiatry, 9(4), 1–3.


Salkovskis, P. M. (1995). Demonstrating specific effects in cognitive and behavioural therapy. In M. Aveline & D. Shapiro (Eds.), Research foundations for psychotherapy practice (pp. 191–228). Chichester, UK: Wiley.

There are many helpful meta-analyses of how well CBT works for different presenting problems. For example this meta-analysis on CBT for PTSD.

Lewis, C., Roberts, N. P., Andrew, M., Starling, E., & Bisson, J. I. (2020). Psychological therapies for post-traumatic stress disorder in adults: systematic review and meta-analysis. European journal of psychotraumatology11(1), 1729633.

LINK: https://www.tandfonline.com/doi/full/10.1080/20008198.2020.1729633

More meta analyses are available by searching Google Scholar.


For more information on specific problems you can also listen to our podcast series, ‘Let’s Talk About CBT’ These have interviews with clinicians and people who have experienced CBT firsthand, and all of the episodes include a brief review of the evidence base for that problem from the clinician involved.

Contributing to the research literature

All these types of research are helpful in different ways, and the scientific basis of CBT depends upon clinicians being involved in research ideas, either in partnership with research teams or as clinical-academic practitioners. You may wish to contribute to the research literature yourself, and the BABCP journals, Behavioural & Cognitive Psychotherapy and The Cognitive Behaviour Therapist, cater for practitioner articles as well as more experimental studies. There are also opportunities to present at the BABCP conferences. It is important if you are undertaking research that you consider any ethical concerns and obtain informed consent from any participants.

More information on research training is available at the following links:

Free online training from the National Institute to Health Research about health research.


For those with some existing knowledge and skills there are the NIHR funds for training


Most universities also provide formal training courses in health research.

Former BABCP President Shirley Reynolds collates some free training resources on research on her website: https://www.drshirleyreynolds.com/research 

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