The Pragmatic Case Study in Psychotherapy: A Mixed Methods Approach Informed by Psychology’s Striving for Methodological Quality

At least as far back as Plato and Aristotle, psychology began as a stepchild of philosophy. The establishment by Wilhelm Wundt in 1879 of the first formal psychological laboratory focused on studying psychophysiological phenomena was psychology’s declaration of independence as a discipline. By positioning itself as the application of natural-science-based, empirical methods involving quantitative, group-based approaches to psychological topics, the discipline consolidated its independence and its societal status and clout. This paper first summarizes these developments, to highlight the causes of psychology’s historical resistance to qualitative case studies, and to qualitative research generally. I then briefly review three movements that have stimulated psychology to slowly but surely embrace qualitative case study research, with the addition of complementary, quantitative data: the rise of postmodern philosophy, the related “cognitive revolution” in psychology, and the “mixed methods” model of research in the social sciences that synergistically combines qualitative and quantitative methods. The result of this embrace, in the context of psychology’s established science-oriented identity, has been for psychology to add quality-of-knowledge guidelines for elevating the yield of case study knowledge. This result is illustrated by three examples: Kazdin’s (J Consult Clin Psychol 49:183–192, 1981) strategies for reducing threats to the validity of conclusions from case studies; Elliott, Fischer, and Rennie’s (Br J Clin Psychol 38:215–229, 1999) development of methodological standards for both quantitative and qualitative research; and my own work in developing the Pragmatic Case Study (PCS), which particularly reflects three of the recent trends in psychology: pluralism, pragmatism, and the mixed methods approach. Comparisons between organized social work’s and organized psychology’s approach to psychotherapy training and research is noted, with the two fields starting off in opposite directions and recently coming together.