Del Re, A.C., Fluckiger, C., Horvath, A.O., Symonds, D., & Wampold, B.E. (2012). Therapist effects in the therapeutic alliance-outcome relationship: A restricted-maximum likelihood meta-analysis. Clinical Psychology Review, 32, 642-649.
The therapeutic alliance, defined as the agreement on tasks and goals and the bond between therapist and patient, is one of the most researched concepts in psychotherapy. A meta-analysis of over 200 studies showed that the association between the therapeutic alliance and patient outcomes is moderate but robust (i.e., consistent across studies, patient types, and therapy types). Some have stated that the importance of the therapeutic alliance as reported in studies is an under-estimate of its real impact on patient outcomes. Del Re and colleagues argue that the main reason for this underestimation is that while the therapist’s effect on the alliance-outcome relationship might be large, the client’s effect might be quite small, and so the average of these two effects (which is what most studies report) will be diminished. Del Re and colleagues conducted the first meta analysis to assess the relative size of therapist versus client effects across many studies. Their strategy was clever. They looked at the ratio of the number of patients to therapists (PTR) within a study as a “predictor” of the alliance-outcome relationship across studies. This allowed them to examine the relative contribution of therapists and clients to the alliance-outcome relationship. Two extreme examples illustrate this ratio. (1) In one study, many patients might have been seen by only one therapist, in which case the alliance-outcome correlation could only be attributed to differences between clients since there was only one therapist. (2) In another study, each client might have been seen by a different therapist (i.e., there were as many therapists as clients), in which case the alliance-outcome correlation could only be attributed to differences between the therapists; that is, there are no differences between clients seen by the same therapist as this did not occur. The patient to therapist ratio (PTR) captures the variability between these two extreme examples across studies. Del Re and colleagues included 69 studies that provided enough information about the number of patients and therapists. The overall correlation between alliance and outcome was moderate, r = .27, which was very similar to what was found in a previous large meta-analysis. PTR was significantly associated with the alliance-outcome relationship even after controlling for a number of possible confounding variables. Patients accounted for almost 0% of the alliance-outcome relationship, whereas the effect of therapists was substantially larger, r = .40, accounting for 16% of the alliance-outcome association.
Therapists’ capacity to develop an alliance with their patients is associated with outcomes. We also know that some therapists demonstrate better patient outcomes than others. So, therapists who consistently are better at forming alliances with patients likely have patients with better treatment outcomes. The quality of the alliance between patients and therapists appears to be the result of what therapists do or bring to the therapy. And so, on average, the therapist’s role in the alliance is most important for achieving good patient outcomes. Del Re and colleagues note that they were not able to look at the interaction between therapist and patient factors. For example, it may be possible that some therapists might form better alliances some types of patients, but not others. Integrating feedback systems so therapists can monitor the therapeutic alliance and patient outcomes may help therapists identify areas in which they need more training or supervision.