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Therapist Effects

Therapist (or clinician) effects refer to the phenomena that practitioners of healing practices (including psychotherapy) differ in their outcomes even when delivering ostensibly identical treatments. In stark statistical terms, often more of the variance in outcomes is due to who does the treatment than to what the treatment is. This is certainly true for psychotherapy, and recent evidence suggests it is also true for pharmacotherapy also. See:

Analysis of large datasets reveals that the distribution of therapist effectiveness is normally distributed, creating the familiar Bell Curve.

Analysis of therapist effects depends upon multilevel modeling, also call hierarchical linear modeling (HLM). Use of HLM permits correct modeling of the variance at the clinician level and treatment level. Use of traditional analysis of variance which does not treat the therapist as a variable tends to result in an over estimate of the treatment effect. Unfortunately, many clinical trails for psychotherapy and almost all pharmacy trials fail to correctly model for therapist effects.

Therapist effects are good news (mostly) for therapists. It means that we are not simply technician delivering well specified and empirically validated treatments. The outcome of mental health treatment depends largely on the effectiveness of the therapist; the treatment requires all of our knowledge, skill, experience, creativity and personal human qualities to be maximally effective.

Other recent publications:

Supershrinks: What is the secret of their success?

Psychotherapy Networker; November/December, 2007
  • Scott Miller, Ph.D.
  • Mark Hubble, Ph.D.
  • Barry Duncan, Ph.D.
This provocative article takes a fresh look at how a therapist can become a "supershrink" by drawing from other research on how top performers in other fields achieve their results. Is it talent or hard work? In any case, performance feedback is critical.

An Analysis of Therapist Treatment Effects: Toward Providing Feedback to Individual Therapists on Their Clients' Psychotherapy Outcome.

Journal of Clinical Psychology, Vol 62(9), Sep 2006. pp. 1157-1172.
  • Okiishi, John C., Brigham Young University, Provo, UT, US
  • Lambert, Michael J., Brigham Young University, Provo, UT, US,
  • Eggett, Dennis, Brigham Young University, Provo, UT, US
  • Nielsen, Lars, Brigham Young University, Provo, UT, US
  • Dayton, David D., Brigham Young University, Provo, UT, US
  • Vermeersch, David A., Loma Linda University, Loma Linda, CA, US
  • Brief Summary: This exciting new study analyzed outcomes from over 5,000 clients seen by 71 therapists over a 6-year period in the Brigham Young University Counseling Center. Data were analyzed using hierarchical linear modeling (HLM) to see if general therapist traits (i.e., theoretical orientation, type of training) accounted for differences in clients' rate of improvement and then again using HLM with therapists as a fixed effect, to evaluate if therapists differed in the efficiency of treatment. General therapist traits did not account for differences in outcome, while a significant amount of variation was found among therapists' clients' rates of improvement. Therapist received feedback on their outcomes as compared to center averages in an attempt to improve client outcome.

Therapist effects in psychotherapy: A random-effects modeling of the National Institute of Mental Health Treatment of Depression Collaborative Research Program data.

Psychotherapy Research, Vol 16(2), Mar 2006. pp. 161-172.

  • Kim, Dong-Min, University of Wisconsin-Madison, Madison, WI, US
  • Wampold, Bruce E., University of Wisconsin-Madison, Madison, WI, US,
  • Bolt, Daniel M., University of Wisconsin-Madison, Madison, WI, US
  • Brief summary: Data for from the two psychotherapy conditions of the National Institute of Mental Health Treatment of Depression Collaborative Research Program were analyzed to estimate the proportion of variability in outcomes resulting from therapists. The results indicated that about 8% of the variance in outcomes was attributable to therapists, whereas 0% was due to the particular treatment delivered. In contrast to previously reported results, when therapist effects were appropriately modeled, differences in efficacy between the two psychotherapy conditions for more severely depressed patients disappeared, as predicted by methodological considerations.

Older publications

Luborsky L, Crits-Christoph P, McLellan T, et al. 1986. Do therapists vary much in their success? Findings from four outcome studies. Am J Orthopsychiatry 56:501-12.

Crits-Christoph P, Baranackie K, Kurcias JS, et al. 1991. Meta-analysis of therapist effects in psychotherapy outcome studies. Psychother Res 1:81-91.

Crits-Christoph P, Mintz J. 1991. Implications of therapist effects for the design and analysis of comparative studies of psychotherapies. J Consul Clin Psychol 59:20-6.

Wampold BE. 1997. Methodological problems in identifying efficacious psychotherapies. Psychother Res 7:21-43,

Elkin I. 1999. A major dilemma in psychotherapy outcome research: Disentangling therapists from therapies. Clin Psychol Sci Prac 6:10- 32.

Wampold BE, Serlin RC. 2000. The consequences of ignoring a nested factor on measures of effect size in analysis of variance designs. Psychol Methods 4:425-33.

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