The Role of Qualitative Methods in Research on Psychotherapy Effectiveness

Entry for 28 December 2009:

Last month Louise Silverstein, of Yeshiva University in New York City, asked me if I would be willing to present as part of a panel on the use of qualitative methods for providing evidence for psychotherapy effectiveness, to be submitted for presentation at the American Psychological Association conference in San Diego next summer. I wrote back as follows:

Do you mean using qualitative methods alone without any quantification? Or using qualitative methods to complement, question, elaborate and/or explain quantitative methods? It seems to me that change in therapy, and therefore by extension effectiveness, is a matter for both quantitative and qualitative data collection and analysis. I am willing to argue along this line for the essential role of qualitative methods in research on the outcome and effectiveness/efficacy of therapy, alongside quantification of amount of change. Would this be of interest or value for your panel?

Fortunately, Louise was happy for me to do this, and I produced the following summary, which I think is worth posting here because of its topical interest, regardless of whether the panel is accepted or not:

* * *

In this presentation I argue that qualitative data collection and analysis methods have several essential roles to play in research on psychotherapy efficacy and effectiveness:

First, qualitative methods enable us to identify the full range of effects of psychotherapy, beyond those assessed by the outcome measures used in any given study (=qualitative outcome research). This allows us to validate, interrogate, elaborate and deepen quantitative outcome findings on the effectiveness of therapy.

Second, qualitative research on what clients find helpful (or hindering) in their therapy provides a basis for making causal inferences about psychotherapy effectiveness and efficacy (=helpful factors research). Client post-therapy (or post-session) accounts of the aspects of therapy they used to change themselves provide one of several genres of psychotherapy change process research (Elliott, 2010).

Third, qualitative methods allow us to construct case studies to exemplify our quantitative outcome findings (=illustrative narrative case studies). Such narrative case studies make quantitative findings available and appealing to practicing therapists, thus enhancing the persuasive appeal of outcome studies.

Fourth, qualitative methods make it possible for us to evaluate effectiveness and efficacy at the single case level (=interpretive or pragmatic case studies). Qualitative methods are essential for constructing rich case records that provide the basis for drawing causal inferences about the role of psychotherapy in client change, as illustrated by Hermeneutic Single Case Efficacy Design studies (Elliott, 2002).

To sum up, it seems to me that establishing the effectiveness of psychotherapy requires mixed methods designs: Quantitative methods are good for measuring the amount of change and its probability, while qualitative methods excel at defining and describing what has changed and providing causal accounts of how change has come about.