Back around 2005, I noticed a gap in the counselling literature: there was no accessible, engaging summary of what the research actually tells us about whether, and how, therapy works. There were plenty of texts on methodology, but nothing that drew together the findings themselves. So I spent a year—bought out by the British Association of Counselling and Psychotherapy—trying to pull it all together, and published Essential Research Findings in Counselling and Psychotherapy (Sage, 2008). Research evidence doesn’t stay fresh forever, and after 15 years of hoping the update would somehow write itself, I finally sat down and researched the second edition. So what has the past decade and a half brought us?

In 2008, I was fairly persuaded that different therapeutic orientations produced broadly equivalent outcomes. Studies claiming superiority for CBT over person-centred therapy (PCT) could largely be accounted for by allegiance effects—the biases of researchers who were typically CBT advocates themselves. But recent evidence suggests that there may be small meaningful differences in outcomes for clients, on average, in different therapies. A particularly important study was the PRaCTICED trial (Barkham et al, 2021): a large pragmatic randomised controlled trial comparing CBT and PCT in real UK health settings, led by researchers with balanced allegiances. At six months, clients in PCT were doing as well as those in CBT. At twelve months, however, those who had received CBT showed somewhat better outcomes on symptoms of depression. This is consistent with findings in the broader field, suggesting that more structured, active therapies may do somewhat better—again, on average—than less therapist-led approaches.

Even so, therapist orientation and techniques is estimated to account for only approximately 10 per cent of change (Norcross & Lambert, 2019), so other factors still have an important role. The person of the therapist is now estimated to contribute about 7 per cent (ibid, 2019), and we now have clearer evidence about which therapist characteristics actually influence outcomes. Therapists with a more secure attachment style and a more affiliative interpersonal manner tend to produce better results overall (Schauenburg et al, 2010, Lingiardi et al, 2018)—especially with clients experiencing high levels of distress, where secure attachment may allow for greater flexibility of response. Therapist wellbeing, as indicated by self-affiliation, has also been linked to improved client outcomes (Heinonen & Nissen-Lie, 2020). Research is also pointing to strong connections between outcomes and therapists’ levels of reflexivity, mindfulness, and emotional intelligence (Cologon et al, 2017). Interestingly, this matters most where therapists carry significant personal vulnerabilities, like insecure attachments.

On professional development, the evidence still suggests that training alone does not reliably translate into better client outcomes—but it does help therapists build specific skills (Teding van Berkhout & Malouff, 2016). The approach showing the most promise here is deliberate practice (Nurse et al, 2024): a structured, effortful focus on developing targeted competencies—such as effective use of silence—with regular feedback through recording review, supervised practice, and repetition.

Evidence is now also mounting for the role of the relationship. We have always known that relationship quality and outcomes correlate, but new ‘longitudinal’ methods are now tracking both variables at multiple points across therapy. This makes it possible to directly test whether improvements in the relationship precede improvements in client wellbeing. And the evidence suggests they do (Flückiger et al, 2019; Zilcha-Mano, 2017). This is still not quite proof of causality, but it is about as close as you can get (bar randomly assigning clients to good and bad quality therapeutic relationships, which may not go down well with an ethics committee).

Advances in qualitative meta-analysis (Timulak, 2009) are also now allowing researchers to understand more about how clients change, by synthesising findings across multiple qualitative studies into coherent conclusions. A recent meta-analysis of data from 17 qualitative studies, for instance, found 12 recurring themes in how clients described the impacts of helpful events in therapy (Ladmanová et al, 2022). These included gaining a fresh perspective on themselves, experiencing relief, developing new skills and coping strategies, becoming more connected with their emotions, and feeling empowered. A broader meta-analysis spanning over 100 studies described the central mechanism of change as clients feeling known and cared for, which enables them to recognise unhelpful patterns in their experience and attend to deeper unmet needs (Levitt et al, 2016).

Perhaps the most important new frontier in the therapy research field is personalisation: matching the type of therapy to the individual client’s characteristics, preferences, and background. Advances in big data and machine learning now allow researchers to identify patterns across hundreds of thousands of clients and develop matching algorithms. Early results are encouraging—small but significant advantages for tailored interventions have been found (Nye et al, 2023;, Delgadillo et al, 2022).

Beyond algorithmic learning, researchers are now understanding more about the particular therapies that may be most helpful for particular groups of clients. Research on culturally adapted therapies—where language, values, and context are systematically modified to fit the client’s cultural background—are now showing meaningful gains over treatment as usual (Soto et al, 2019). Similar effects have emerged for therapies adapted to clients’ religious or spiritual frameworks (Hook et al, 2019). Qualitative studies add nuance: clients from disabled and neurodiverse communities report that being seen within their actual context matters enormously. One client described the worst aspect of their therapy as a complete disregard for their disability—being encouraged to do things their condition made impossible (Olkin & Gomez, 2024). Two personality dimensions also appear to moderate treatment response. First, clients who are more reactant (resistant to being told what to do) tend to fare better in less directive therapies, while those who are more compliant do better with more structured methods (Edwards et al, 2019). Second, clients with more internalised coping styles tend to benefit more from insight-oriented approaches such as psychodynamic therapy, while those with externalised styles tend to respond better to symptom-focused methods like CBT (Beutler et al, 2019). Across the board, clients who receive therapy aligned with their own stated preferences show better outcomes and are more likely to stay in treatment (Swift et al, 2019).

The second edition of Essential Research Findings in Counselling and Psychotherapy brings together a wealth of new evidence, much of which deeply validates the work that we do. But for therapists of every orientation, there will also be findings that surprise, challenge, and perhaps provoke us to develop our work in new ways. Nevertheless, as Carl Rogers (1961) says, ‘the facts are always friendly. Every bit of evidence one can acquire, in any area, leads one that much closer to what is true. And being closer to the truth, however uncomfortable at times, is never a bad place to be.

Mick Cooper is Professor of Counselling Psychology at the University of Roehampton, a chartered psychologist, and father of four living on the south coast of England. His principal areas of research have been shared decision-making and person-centred counselling for young people.

Barkham, M., Saxon, D., Hardy, G. E., et al. (2021). Person-centred experiential therapy versus cognitive behavioural therapy delivered in the English Improving Access to Psychological Therapies service for the treatment of moderate or severe depression (PRaCTICED): a pragmatic, randomised, non-inferiority trial. The Lancet Psychiatry, 8(6), 487-499. https://doi.org/10.1016/S2215-0366(21)00083-3

Beutler, L. E., Edwards, C. J., Kimpara, S., et al. (2019). Coping style. In J. C. Norcross & B. E. Wampold (Eds.), Psychotherapy relationships that work (3rd ed., Vol. 2: Evidence-based therapist responsiveness, pp. 56-85). Oxford University.

Cologon, J., Schweitzer, R. D., King, R., et al. (2017). Therapist Reflective Functioning, Therapist Attachment Style and Therapist Effectiveness. Adm Policy Ment Health, 44(5), 614-625. https://doi.org/10.1007/s10488-017-0790-5

Delgadillo, J., Ali, S., Fleck, K., et al. (2022). Stratified care vs stepped care for depression: A cluster randomized clinical trial. JAMA Psychiatry, 79(2), 101-108. https://doi.org/10.1001/jamapsychiatry.2021.3539

Edwards, C. J., Beutler, L. E., & Someah, K. (2019). Reactance level. In J. C. Norcross & B. E. Wampold (Eds.), Psychotherapy relationships that work (3rd ed., Vol. 2: Evidence-based therapist responsiveness, pp. 188-211). Oxford University.

Flückiger, C., Del Re, A. C., Wampold, B. E., et al. (2019). Alliance in adult psychotherapy. In J. C. Norcross & M. J. Lambert (Eds.), Psychotherapy Relationships that Work: Evidence-based responsiveness (3rd ed., pp. 24-78). Oxford University.

Heinonen, E., & Nissen-Lie, H. A. (2020). The professional and personal characteristics of effective psychotherapists: a systematic review. Psychotherapy Research, 30(4), 417-432. https://doi.org/10.1080/10503307.2019.1620366

Hook, J. N., Captari, L. E., Hoyt, W., et al. (2019). Religion and spirituality. In J. C. Norcross & B. E. Wampold (Eds.), Psychotherapy relationships that work (3rd ed., Vol. 2: Evidence-based therapist responsiveness, pp. 212-263). Oxford University.

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Lingiardi, V., Muzi, L., Tanzilli, A., et al. (2018). Do therapists' subjective variables impact on psychodynamic psychotherapy outcomes? A systematic literature review. Clinical Psychology & Psychotherapy, 25(1), 85-101. https://doi.org/https://doi.org/10.1002/cpp.2131

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Nye, A., Delgadillo, J., & Barkham, M. (2023). Efficacy of personalized psychological interventions: A systematic review and meta-analysis. Journal of Consulting and Clinical Psychology, 91(7), 389-397. https://doi.org/10.1037/ccp0000820

Olkin, R., & Gomez, M. (2024). Experiences of physically disabled and blind people in psychotherapy: Lessons for CBT therapists. the Behavior Therapist, 47(1), 8-21.

Rogers, C. R. (1961). On becoming a person: A therapist's view of therapy. Constable.

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Swift, J. K., Callahan, J. L., Cooper, M., et al. (2019). Preferences. In J. C. Norcross & B. E. Wampold (Eds.), Psychotherapy relationships that work (3rd ed., pp. 157-187). Oxford University.

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Zilcha-Mano, S. (2017). Is the alliance really therapeutic? Revisiting this question in light of recent methodological advances. American Psychologist, 72(4), 311-325. https://doi.org/10.1037/a0040435