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Estimating and Understanding Therapist Effects

Estimating and Understanding Therapist Effects. Empirical Evidence. Bruce E. Wampold University of Wisconsin--Madison. History of Omission. Historically, provider effects ignored Education Agriculture Medicine. Ignoring Therapists. Therapists unimportant Therapist effects not estimated

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Estimating and Understanding Therapist Effects

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  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 • 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. Greater Severity Greater Severity 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

  10. Variance due to Tx and Therapists

  11. Variance due to Tx and Therapists 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

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