Office in Walnut Creek, California CA
Jay Slupesky, M.A., MFT
In testing the effectiveness of psychotherapy, the efficacy study is the more popular method and the one traditionally more trusted by researchers (Seligman, 1995). Efficacy studies are highly controlled and methodological: the psychotherapy being tested is used with one group of patients, while other control groups undergo either no treatment or treatment with credible placebos. The patients selected to participate in an efficacy study must be suffering from a particular disorder, and any patient with multiple disorders is usually not included. Participating therapists are given detailed instructions and continuing guidance on how to perform the therapy and patients are seen for a relatively small (twelve, for example) number of sessions. Although the therapists and patients involved are of course aware of what type of treatment they have been through, the diagnosticians who test, interview, and evaluate are blind to which group a patient belongs to. The diagnosticians continue to evaluate the patients for some time after therapy has ended. Not surprisingly, efficacy studies are time-consuming and expensive.
In contrast to the efficacy study, an effectiveness study looks at how much benefit "actual" patients gain from "real-life" therapy. Patients who have already begun (and possibly completed) therapy are surveyed by researchers and asked detailed questions about their treatment and its effectiveness. Unlike the efficacy study, in an effectiveness study the researchers have no say in how therapy is performed, nor can they select which patients undergo which type of therapy or which therapist a patient sees. Therefore, the researchers cannot create a control group to use as a baseline and there are no placebo therapies. Patients with multiple disorders cannot be excluded from an effectiveness study. Since the patients who are surveyed for the study have already begun and possibly also completed therapy, much (if not all) of the therapy takes place with neither the therapist nor the patient even knowing that they will be part of a study.
As mentioned, efficacy studies are usually time-consuming and expensive. However, since effectiveness studies are essentially surveys, they are much less time-consuming and less expensive to perform. Due to the low cost per participant, an effectiveness study can be performed on a much larger population of subjects. Also, because of the expense and effort required, the efficacy study is typically done over a relatively short and fixed number of sessions. Clearly, this is different from the real world because real people initiate therapy and stay involved in it for varying lengths of time; those with sufficient resources may stay in therapy for years and may improve throughout that time. Seligman (1995) asserts that most of the psychotherapy done in the field today cannot be tested in efficacy studies due to the long-term nature of popular therapies. Long-term patients are easily included in an effectiveness study, and this fact alone adds value to the effectiveness study method.
There are some problems with effectiveness studies, however. They have a sampling bias because participants are both self-selecting when initiating therapy and then are self-selecting again when electing to participate in the survey or not. This means that effectiveness studies cannot be done on random population samples. Also, effectiveness studies rely on the retrospective observation of the participants; some time may have elapsed since they terminated therapy, hindering the accuracy of their memories, or even worse, they may intentionally give false answers to survey questions. Even with these limitations in mind, Seligman (1995) argues that the advantages of efficiency studies outweigh their limitations, and that efficiency studies are undervalued and underused by psychotherapy researchers.
2004 Nov 4