Research Article: The Relationship Between Therapist Effects and Therapy Delivery Factors: Therapy Modality, Dosage, and Non-completion

Date Published: July 16, 2016

Publisher: Springer US

Author(s): David Saxon, Nick Firth, Michael Barkham.


To consider the relationships between, therapist variability, therapy modality, therapeutic dose and therapy ending type and assess their effects on the variability of patient outcomes. Multilevel modeling was used to analyse a large sample of routinely collected data. Model residuals identified more and less effective therapists, controlling for case-mix. After controlling for case mix, 5.8 % of the variance in outcome was due to therapists. More sessions generally improved outcomes, by about half a point on the PHQ-9 for each additional session, while non-completion of therapy reduced the amount of pre-post change by six points. Therapy modality had little effect on outcome. Patient and service outcomes may be improved by greater focus on the variability between therapists and in keeping patients in therapy to completion.

Partial Text

The past 50 years has seen a concerted effort by researchers to develop more effective models of therapy. The dominant research method for testing the efficacy of such models has been the randomised controlled trial (RCT) and results have been summarised by national policy bodies [e.g., Substance Abuse and Mental Health Services Administration (SAMDSA), National Institute for Health and Care Excellence (NICE)] to support the adoption of efficacious, evidence-based treatments into routine clinical practice. For example, the Australian Department of Health requires Medicare-funded treatments to be evidence-based (Department of Health 2012), and treatment provision decisions made by the American Medicare and Medicaid governmental programs are influenced by the AHRQ (Agency for Healthcare Research and Quality 2002).

Our primary measure was the Patient Health Questionnaire-9 (PHQ-9; Kroenke et al. 2001). The PHQ-9 is a nine item measure of depression. Each item is rated from 0 to 3. Scores can range from 0 to 27, with higher scores indicating more symptoms of depression. The primary outcome was the pre-post change on the PHQ-9. Therefore, positive values were indicative of patient symptom improvement, whilst negative values indicated that their symptoms had worsened.

In this study of the variability of patient outcomes in naturalistic settings we sought to use practice-based evidence to complement the evidence-based research that informs policy, guidelines and service delivery. Using multilevel modeling to identify more and less effective therapists controlling for case-mix, we went on to consider therapist variability and outcomes in relation to three delivery factors: treatment modality, dosage and therapy ending. Our results indicate that differences between two evidence-based therapy models were less important for patient outcomes than the individual therapist they see, differences in dosage and in particular, whether the patient completed therapy or not. We also found that the effect that dose and ending type had on patient outcomes varied between therapists.

We found significant variability between therapists’ outcomes after controlling for case-mix and that the effect on outcomes of sessions attended and patient drop-out, varied between therapists. More effective therapists were found to have fewer therapy dropouts and be more effective with therapy completers than less effective therapists. For therapy completers, more effective therapists delivered one more session on average than less effective therapists and were able to achieve greater change per session.




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