Placebos and common factors in two decades of psychotherapy research.

Abstract

Two decades of psychotherapy research conceptualizing placebos as variables common across psychotherapies are reviewed. Placebo treatments and placebo controls have been thought to be composed of factors common across psychotherapies by definition. Little empirical support, howevei; was found for this view. The components of placebo controls are not necessarily common with but are often very diiferent from the components of designated therapies. A review was also conducted of the more obvious as well as the more subtle sources of noncontrolled variables that may differentially enter therapeutic conditions. The types of placebo control groups most often used in the literature are not adequate to control the effects of various so-called nonspecific variables or to test the active elements of psychotherapies. Two types of placebo groups were found to be the most appropriate to control for confounding variables in the study of psychological processes and active therapeutic components.Traditionally, psychotherapies and placebos have been thought to belong to two different classes of treatments. In this view, therapies are unique and individual forms of treatments with mechanisms specific to some theoretical conceptualization, but placebos are composed of factors that are common to most types of therapy (Basham, 1986;Critelli & Neumann, 1984;O'Leary & Borkovec, 1978). It has been pointed out that placebo components are assumed to be common to the designated therapy and placebo control by definition (Wilkins, 1983). In addition, placebos are seen as having less specific or focused effects than legitimate psychotherapies (Shapiro & Morris, 1978). Both of these assumptions are overgeneralizations. This article presents an investigation of the nature of placebo controls and components based on their use in the literature. The review of two decades of the use of placebo controls in psychotherapy research indicates that the assumption that placebos are composed of common variables across therapies is not reflected in research designs. Therapies and placebo controls do not share common elements in a large proportion of the reviewed studies.Conditions that have been designated at one time or another as placebo components also vary considerably across therapies and are as unique as psychotherapy components. Placebos, like psychotherapies, have effects that are on target as well as effects that are off target or outside the specified problem. To the extent that both psychotherapies and placebos have clinically significant effects that are on target, they are legitimate forms of ther-

Designing a Control for a Behavioral Group Therapy

“…Methodological issues concerning the concept of a common factors control group have been raised in a number of thoughtful critiques (Baskin et al, 2003;Chambless & Hollon, 1998;Critelli & Neumann, 1984;Horvath, 1988;Lohr et al, 2003;Parloff, 1986;Stevens et al, 2000). For example, while there appears to be agreement that common factors exist across psychotherapies (Weinberger, 1993), there is a lack of agreement over what they are, what they should be termed (e.g.…”

“…For example, while there appears to be agreement that common factors exist across psychotherapies (Weinberger, 1993), there is a lack of agreement over what they are, what they should be termed (e.g. "nonspecific" factors, "common factors," "placebo effects"), how they should be operationally defined (Horvath, 1988), which factors are most important, how they are interrelated, and whether they can be reliably measured (Messer & Warren, 1995).…”

“…therapeutic alliance, therapeutic rationale, etc.) on outcome, a comparison group must possess these general therapeutic factors while omitting the unique active ingredients of the treatment under investigation (Horvath, 1988;Stevens et al, 2000). As Stevens et al (2000) assert: "The task of demonstrating that specific techniques in complete treatments exceed common factors requires outcome studies that compare complete treatments with common factor controls.…”

“…Reviews of the controlled-trial psychotherapy research literature show that systematic matching is not a customary practice (Baskin, Tierney, Minami, & Wampold, 2003;Critelli & Neumann, 1984;Horvath, 1988;Stevens et al, 2000). Rather than precisely controlling for the common factors across psychotherapies, researchers typically use waiting lists, educationally focused groups, dissimilar comparative treatments, and treatment as usual for this purpose.…”

“…The specific therapeutic effect of a group psychotherapy treatment is most rigorously evaluated when the treatment under investigation is as closely matched as possible to a randomly assigned comparison treatment group (see for example Horvath, 1988;Lohr, DeMaoi, & McGlynn, 2003;Stevens, Hynan, & Allen, 2000). To control for the effects of the common factors (e.g.…”