“When I was trained as a psychotherapist, I learned that change in psychotherapy is caused for 15% by specific therapeutic techniques, 30% by common factors, 15% by expectancy effects, and 40% by extra-therapeutic factors. Is that true? A colleague of mine said that this is not based on empirical data.”
Where these numbers come from
These numbers come from an influential article by Lambert that was published more than 30 years ago, in 1992. Since then, these numbers are often given as a pie chart in many handbooks and training materials for clinicians. And, unfortunately, they are still used today in many training materials. These numbers and the pie chart appeal to many clinicians due to their simplicity (echoing the sentiment that “it’s all about the relationship”).
Why the pie chart does not hold up
However, these numbers are not based on any empirical data, and are in fact no more than rough estimates of correlates based on impressions from the literature. There is no empirical evidence to support the percentages given in the chart.
There is also a more basic problem with the interpretation of these numbers. The problem is that the four components are not mutually exclusive. For example, the therapeutic relationship can influence expectancy; a specific therapeutic technique can strengthen the alliance; patient characteristics can influence both the alliance and the response to specific techniques.
What the data can (and cannot) tell us
There are some numbers from empirical studies that could be used to make some rough estimates about what causes change, but only when one is prepared to allow for the many uncertainties and flaws of making such estimates.
In one older meta-analysis, we examined the effects of supportive counseling for depression compared to other therapies and to control conditions (Cuijpers et al., 2012). Although this is all very hypothetical, uncertain and imprecise, one could assume that what happens in the control conditions from baseline to post-test is the ‘extra-therapeutic factors’ from Lambert, because that is the improvement that happens anyway, outside therapy. Based on our meta-analysis, we would estimate that 40% is caused by extra-therapeutic factors. The additional change in supportive therapy can be considered as caused by the therapeutic relationship and patient expectations; in our meta-analysis that was 50%. The specific techniquesThe additional effects of specific therapies above those of supportive counseling. were responsible for 17%.
However, nowadays we have more specific data on improvement during therapy. The most important difference between both Lambert’s estimates and our meta-analysis is that we now know that there is no improvement at all in many patients. As much as 58% of patients who get therapy do not respond — only 42% doResponse defined as a 50% symptom reduction from the start to the end of therapy.. Of patients receiving no treatment about 17% respond, and those who receive pill placebo 31%. This means that specific and non-specific factors together can explain 11% of response (42 minus 31%). Based on these data, it is not possible to estimate the separate contribution of specific and non-specific factors. But, as indicated earlier, these numbers should not be used in this way, and can indicate sources of improvement only very roughly and with (too) many uncertainties.
The group the pie chart forgets
It should also be kept in mind that there is a small, but important, minority of patients who deteriorate during therapy. That has no place at all in the overview of Lambert, but clinically this is an important group. About 5% of patients deteriorate further during therapy. This percentage is higher when patients are not treated (12 to 13%), but it is still something that needs to be kept in mind when discussing improvement.
In summary
The most important conclusion is that the original overview of sources of improvement from Lambert is not based on empirical data and should not be used at all — also because the sources of improvement are not mutually exclusive.
More important, however, is that it suggests that change happens in all patients in therapy. But that is not the case. Many patients do not respond, and there is even a small group of patients who get worse during therapy. It is more important to be aware of this than to think about hypothetical and unclear sources of potential improvement.
- For whether therapies really differ in their effects, see Are all psychotherapies equally effective?
- For why an evidence-based treatment can still fail a patient, see Why does a treatment not work, while it is evidence-based?
- For the role of the relationship, see Is the therapeutic alliance the most important part of therapy?
Pim Cuijpers is professor emeritus of clinical psychology and scientific director of Metapsy. He has been involved in more than 1,100 scientific studies, mostly on psychological treatments of mental health problems. This is one of a series of evidence summaries in which Prof. Cuijpers tries to answer questions from patients and clinicians, based on what is known in science about treatments. The knowledge is mostly drawn from collective work of the Metapsy collaboration of at least 15 years. Do you have other questions you would like Prof. Cuijpers to discuss? Feel free to contact us.
Literature
- Lambert MJ. (1992). Psychotherapy outcome research: Implications for integrative and eclectic therapists. In: JC Norcross & MR Goldfried (Eds.), Handbook of Psychotherapy Integration (pp. 94–129). New York: Basic Books.
- DeRubeis RJ, Gelfand LA, German RE, Fournier JC, Forand NR. (2014). Understanding processes of change: How some patients reveal more than others — and some groups of therapists less — about what matters in psychotherapy. Psychotherapy Research, 24(3), 419–428.
- Cuijpers P, Driessen E, Hollon SD, van Oppen P, Barth J, Andersson G. (2012). The efficacy of non-directive supportive therapy for adult depression: a meta-analysis. Clinical Psychology Review, 32(4), 280–291.
- Cuijpers P, Karyotaki E, Ciharova M, Miguel C, Noma H, Furukawa TA. (2021). The effects of psychotherapies for depression on response, remission, reliable change, and deterioration: A meta-analysis. Acta Psychiatrica Scandinavica, 144(3), 288–299.
- Cuijpers P, Reijnders M, Huibers MJH. (2019). The role of common factors in psychotherapy outcomes. Annual Review of Clinical Psychology, 15(1), 207–231.
