Some methodological and statistical issues in the study of change processes in psychotherapy

Abstract

As the number of psychotherapies with demonstrated efficacy accumulates, an important task is to identify principles and processes of change. This information can guide treatment refinement, integration, and future development. However, the standard randomized control trial (RCT) design can limit the questions that can be asked and the statistical analyses that can be conducted. We discuss the importance of examining the shape of change, in addition to identifying mediators and moderators of change. We suggest methodological considerations for longitudinal data collection that can improve the kinds of therapy process questions that can be examined. We also review some data analytic approaches that are being used in other areas of psychology that have the potential to capture the complexity and dynamics of change in psychotherapy.The central question of interest in the study of psychotherapy is change over time. Patients come into therapy with certain behavioral, emotional, and/or cognitive difficulties, and they seek relief from these problems and an improved quality of life by the time therapy is completed. One way to determine this change is to assess problems prior to treatment (point A) and at the end of treatment (point B). When it comes to understanding change in psychotherapy, is it enough to know simply that there has been improvement from point A to point B? Process researchers argue no-that is, in addition to knowing that change occurs in response to a treatment, it is crucial to understand how individuals change from point A to point B. We present some important methodological issues to consider to improve the quality of data and statistical analyses in studies of change in clinical trials.In the first section of this paper, we briefly describe the types of questions that can be the focus of process research. In the second section, we discuss some of the ways in which the standard outcome study design, the randomized control trial (RCT) design, can limit the types of process questions that can be asked and the statistical analyses that can be conducted. We present two methodological recommendations that can address some of these limitations. First, we recommend that psychotherapy researchers increase the number of repeated assessments of symptoms and putative mediators or covariates of change over the course of treatment and follow-up. Second, we recommend that psychotherapy researchers carefully consider the timing of the effect of an intervention so that assessments are taken over an appropriate period.In the third section of this paper, we follow these methodological issues with a description of what might be considered the current statistical state of the art in assessing change and Correspondence regarding this paper can be addressed to Jean-Philippe Laurenceau,

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