What are the different types of studies taken from the literature to evaluate the psychotherapies?
Evaluation of the efficacy of a treatment relies on comparative controlled trials. It is practically impossible, however, to compare an active psychotherapy with a psychotherapeutically inert “placebo” in a double-blind, randomised trial based on the models of pharmacological trials, because relationship and situation effects and the expectations of the therapists and patients are active components in any psychotherapeutic system. Different types of “control group” are therefore found in trials, such as the “placebo attention” group, in which the patients have minimal contact with the therapist, who does not use the factors that are assumed to be active in the therapy in question. This helps to remove simple patient management effects. We also see, as a comparison group, the group of patients still on the waiting list, which only receives simple telephone contact for several months (this may raise ethical problems and often results in drop-outs to another therapy). It is common in tria
