1. Estimating and Understanding Therapist Effects
Empirical Evidence
Bruce E. Wampold
University of Wisconsin--Madison

2. History of Omission Historically, provider effects ignored Education
Agriculture
Medicine

3. Ignoring Therapists Therapists unimportant Methodological issues
Therapist effects not estimated
Focus on treatment
Methodological issues
Differences among treatments may be due to therapists
Increases Type I error rate and effect size for Tx effects
Confounds within and between group relationships

4. Goals How important is the provider relative to the treatment?
Estimate the variability among therapists (within treatments)
Therapist variability v. treatment variability
Understand the characteristics and actions of effective therapists
Discriminate between patient and therapist contributions to outcomes

5. Estimating Therapist Effects
Sources of variability:
Treatment differences (fixed effect) αj
Therapist variability (random effect) σ2ther
Error or patient variability σ2error
Therapist Effects:
intraclass correlation coefficient
(Therapist variability) / (Total Variability)
ρ = σ2ther/(σ2ther + σ2error)

6. Effects as Percentage of Variability of Termination Score
Pretest – 40% to 50%
Tx v. No Treatment– about 13%
Treatment A v. Treatment B– at most 1%
Alliance– 5% to 9%
Therapist….
9% (Chrits-Christoph et al., 1991)

7. NIMH TDCRP reanalysis Nested Design (CBT and IPT)
Well trained therapists, adherence monitored, supervision
Elkin:
The treatment conditions being compared in this study are, in actuality, “packages” of particular therapeutic approaches and the therapists who choose to and are chosen to administer them…. The central question… is whether the outcome findings for each of the treatments, and especially for differences between them, might be attributable to the particular therapists participating in the study.

8. Random Effects Modeling
Therapists considered a random factor
Therapists nested within treatments (multilevel model)
Final observations, controlling for pretest at patient and therapist level
Kim, Wampold, & Bolt, Psychotherapy Research, 2006

9. Random Effects Modeling
Therapists considered a random factor
Therapists nested within treatments (multilevel model)
Final observations, controlling for pretest at patient and therapist level
Therapist slope fixed and random
Kim, Wampold, & Bolt, Psychotherapy Research, 2006
Greater Severity

10. Variance due to Tx and Therapists
Variable
Treatment
Therapist
BDI 0%
HRSD
HSCL-90
GAS

11. Variance due to Tx and Therapists
Variable
Treatment
Therapist
BDI 0%
5% - 12%
HRSD
7% - 12%
HSCL-90
4% - 10%
GAS
8% - 10%
Note: Elkin et al. (2006) found negligible therapist effects in the same data

12. Variance due to therapists in practice
581 Therapists, 6146 patients
More heterogeneous patients
Outcome Questionnaire 30
Diagnosis, degree, experience, 0 percent
Medication, 1 percent (but dependent on psychotherapist)
5 percent
Wampold & Brown, JCCP, 2005

13. Cross-validation: year 1 to year 2
At least 9 cases in yr 1
73 Therapists

14. Therapist Effects in Psychopharmacology (NIMH)
Antidepressants: Imipramine v. Placebo
3% due to treatment
9% due to therapist
Best therapists get better outcome with placebo that worst therapists with imipramine
McKay, Imel & Wamold, 2006

15. Therapists– Psychopharm

16. Conclusions Therapists make a difference
Size of therapists effects at least an order of magnitude greater than treatment effects
What are the characteristics or actions of effective therapists?

17. Characteristics and Actions of Effective Therapists
Consult Buetler (Handbook of Psychotherapy and Behavior Change)
We don’t know
And we don’t care
Alliance?
Alliance measured early in therapy related to outcome
Therapist contribution?
Patient contribution?
Interaction?

18. Alliance: Patient v. Therapist Contribution to Alliance
Counseling center consortium data
OQ pre and post, Alliance 4th session
188 patients, 22 therapists
5% of variance due to therapists
What is correlation of alliance with outcome
Within therapists?
Between therapists?
And the results….

19. Within or between?

20. Size of Effect

21. Conclusions Method is vital to proper conclusions
Improper models affect results
Therapist effects are sizable, especially compared to treatment differences
Every process and outcome study MUST include therapists in the model
Multilevel modeling can answer the fundamental question