Bell, E. C., Marcus, D. K., & Goodlad, J. K. (2013). Are the parts as good as the whole? A meta-analysis of component treatment studies. Journal of Consulting and Clinical Psychology, 81, 722-736.
Component studies (i.e., dismantling treatments or adding to existing treatments) may provide a method for identifying whether specific active ingredients in psychotherapy contribute to client outcomes. In a dismantling design, at least one element of the treatment is removed and the full treatment is compared to this dismantled version. In additive designs, an additional component is added to an existing treatment to examine whether the addition improves client outcomes. If the dismantled or added component is an active ingredient, then the condition with fewer components should yield less improvement. Among other things, results from dismantling or additive design studies can help clinicians make decisions about which components of treatments to add or remove with some clients who are not responding. For example, Jacobson and colleagues (1996) conducted a dismantling study of cognitive-behavioral therapy (CBT) for depression. They compared: (1) the full package of CBT, (2) behavioral activation (BA) plus CBT modification of automatic thoughts, and (3) BA alone. This study failed to find differences among the three treatment conditions. These findings were interpreted to indicate that BA was as effective as CBT, and there followed an increased interest in behavioral treatments for depression. However, relying on a single study to influence practice is risky because single studies are often statistically underpowered and their results are not as reliable as the collective body of research. One way to evaluate the collective research is by meta analysis, which allows one to assess an overall effect size in the available literature (see my November, 2013 blog on why clinicians should rely on meta analyses). In their meta analysis, Bell and colleagues (2013) collected 66 component studies from 1980 to 2010. For the dismantling studies, there were no significant differences between the full treatments and the dismantled treatments. For the additive studies, the treatment with the added component yielded a small but significant effect at treatment completion and at follow-up. These effects were only found for the specific problems that were targeted by the treatment. Effects were smaller and non-non-significant for other outcomes such as quality of life.
Psychotherapists are sometimes faced with a decision about whether to supplement current treatments with an added component, or whether to remove a component that may not be helping. Adding components to existing treatments leads to modestly improved outcomes at least with regard to targeted symptoms. Removing components appears not to have an impact on outcomes. The findings of Bell and colleagues’ (2013) meta analysis suggest that specific components or active ingredients of current treatments’ have a significant but small effect on outcomes. Some writers, such as Wampold, have argued that the small effects of specific components highlight the greater importance of common factors in psychotherapy (i.e., therapeutic alliance, client expectations, therapist empathy, etc.). This may be especially the case when it comes to improving a patient’s quality of life.
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