The evaluation of psychological treatment
Authors: Crits-Christoph Paul , Gibbons Mary Beth Connolly 
Published: January 2013

Psychotherapy continues to be a widely practised treatment for psychiatric disorders and other problems in living. Since publication in 1952 of the well-known article by Hans Eysenck, in which he claimed that there was no evidence that psychotherapy was effective, there has been an accelerating literature concerned with methodologies for evaluating psychotherapy, as well as specific studies demonstrating the efficacy, or lack thereof, of various psychotherapies. In more recent years, pressures from the government agencies and insurance companies that bear much of the cost of mental health treatments have added to the call for accountability regarding psychotherapeutic treatment. Despite a vast literature of over 1000 outcome studies of the effects of psychotherapy, questions remain about the role of psychotherapy as a treatment for mental disorders. Extensive meta-analytical reviews of the psychotherapy outcome literature provided evidence that, generally speaking, psychotherapy appears to be efficacious. While encouraging, this information was not particularly useful. As with any medical problem or disorder, the relevant public health clinical question is whether a treatment is beneficial for the presenting problem or psychiatric disorder for which help is sought. Along these lines, a number of efforts have been made at summarizing the results of the psychotherapy outcome literature in terms of what works for different disorders or problems. For example, these efforts have arrived at conclusions such as ‘cognitive therapy is efficacious in the treatment of major depressive disorder’. The simplicity and clinical appeal of such conclusions, about which psychotherapy treatments work for which patient problems, belies a host of more complex issues regarding how one evaluates psychotherapy and makes a decision about whether treatment ‘works’ or not. Other treatments within psychiatry, such as pharmacotherapy, lend themselves to rather straightforward designs (namely placebo-controlled randomized clinical trials) that permit clear inferences about the efficacy of a treatment approach. In contrast, research on psychotherapy as a verbal interchange between two or more participants does not have the luxury of such straightforward pharmacotherapy research designs. Instead, psychotherapy outcome research is characterized by the use of a variety of research designs and methods that, while often not without limitations to strong scientific inferences about treatment efficacy, can provide incremental scientific advance in the understanding of the usefulness of psychotherapeutic treatments. The aim of the current chapter is to provide an overview of approaches to the evaluation of psychological treatments. We begin with a discussion of specific research designs employed in psychotherapy outcome research, with a discussion of some of the broad issues that currently guide the selection among these different experimental designs. This is followed by a selective review of assessment strategies for outcome evaluation, with discussion of examples of instruments.