Missing Outcome Data in a Naturalistic Psychodynamic Group Therapy Study

Hans Henrik Jensen,Martin Lotz,Erik Lykke Mortensen

doi:10.4236/psych.2017.83027

Abstract

We examine project drop-out in 39 sessions of psychodynamic group therapy. A total of 327 patients were included in the project, but 25.4% (83) did not evaluate outcome. According to therapists’ evaluation only 25.3% of the project drop-outs “improved” in “symptoms and problems” as compared with 79.1% of the project responders. According to Jacobson & Truax’s classification of Reliable Change, 52.9% of the project responders had a reliable improvement in the SCL-90 R Global Severity Index (GSI). Based on the relationship between therapist evaluations and GSI we estimated that only 43.7% of the whole samples might have had a reliable improvement in GSI. The SPSS standard statistical imputations procedure estimated that 48.6% of the patients reliably improved in GSI, and 50.2% when therapist evaluations were not included. It is concluded that therapist evaluations are essential in order to avoid bias in reported outcome solely based on project responders in the present naturalistic study, where outcome data probably are missing not at random.

Highlights

In contrast to many randomized controlled trials (RCTs), the naturalistic prepost design evaluates outcome of psychological treatment in a real world setting, where patients are referred to therapy in standard clinical practice (Leichsenring & Rabung, 2007; Nathan, Stuart, & Dolen, 2000)
According to Therapist Retrospective Outcome Evaluation questionnaire (ThROE), only 25.3% (21) of the project drop-outs improved as compared with 79.1% (193) of the project compliant patients (Chi-square 80.15, p < 0.001)
This implies that a ratio of 0.668 (129/193) of the patients who improved according to ThROE reliably changed in Global Severity Index (GSI)

Summary

Introduction

In contrast to many randomized controlled trials (RCTs), the naturalistic prepost design evaluates outcome of psychological treatment in a real world setting, where patients are referred to therapy in standard clinical practice (Leichsenring & Rabung, 2007; Nathan, Stuart, & Dolen, 2000). Schlomer, Bauman, & Card (2010) found that only 38% of outcome studies published in the Journal of Counseling Psychology in 2008 reported percentages of missing data, and only one reported the method to handle this problem. There are no universal agreed criteria for acceptable rates of project drop-out, but rates of 20% - 50% have been suggested as acceptable in epidemiological cohort studies (Fewtress, Kennedy, Singhal, Martin, Ness et al, 2008). This, may be a substantial loss of data in most naturalistic studies of outcome of psychotherapy. Kristman, Manno, & Côte (2004) presented evidence that acceptable rates may depend on different mechanisms, and that data not missing at random in epidemiological studies will result in a significant bias even when 20% of the population is lost. Generalization from outcome studies, including RCTs, should be preceded by a careful examination of the “missingness mechanism(s)” (Bell, Kenward, Fairclough, & Horton, 2013)

Methods

Results

Discussion

Conclusion