Clinical summary: Therapists Differ in Their Effectiveness

Researchers and clinicians have been talking for decades about therapist effects – that is, that therapists are not equally effective. As early as the 1970s, researchers were interested in understanding the difference between more effective and less effective therapists. The evolution of manualized therapies was supposed to reduce differences between therapists by standardizing the treatments, but this reduction was never realized. In one study, clients seen by the most effective therapists achieved three times as much change as compared to those clients seen by the least effective therapists. Quantifying this effect has been challenging because it is difficult to separate the effects of the therapist, the effect of the treatment, and the effect caused by differences between clients. However, with modern statistical techniques, researchers have been able to isolate the therapist effect. In this systematic review, Johns and colleagues provide an update to a previous review conducted by Baldwin and Imel in 2013. Johns and colleagues reviewed studies between 2012 and 2016 that reported therapist effects using the new statistical procedures. The authors identified 20 new articles that met their inclusion criteria. Three studies were highly controlled randomized trials and 17 were studies done in routine clinical practice. The most common presenting client diagnoses were anxiety and depression. The average therapist effect across all studies was 5.0%. That is, about 5% of client outcomes were attributable to differences between therapists. The results were highly variable across studies, but the differences between therapists occurred across a wide range of clinical settings and patient groups. The best predictor of therapist effects was patient severity, such that outcomes across therapists were more variable with more severely symptomatic patients.

Practice Implications

Some therapists are more effective than others. Although 5% may seem small relative to the effect of patient variability, the research appears to indicate that some therapists are consistently more than twice as effective as others even after controlling for patient severity, size of caseload, and other factors. Therapists should track their client outcomes relative to their peers using a wide range of outcome indices like dropout and clinical change on standardized measures. Therapists can use this information to help them with continuing education and supervision. When possible, allocating clients to therapists should consider patient severity. That is, it makes most sense for the most effective therapists to see patients with greater symptoms severity.

Johns, R.G., Barkham, M., Kellett, S., & Saxon, D. (2019). A systematic review of therapist effects: A critical narrative update and refinement to Baldwin and Imel’s (2013) review. Clinical Psychology Review, 67, 78-93. https://doi.org/10.1016/j.cpr.2018.08.004

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