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Efficacy, Effectiveness, and Patient-Focused Research

Description of the Strategy

Psychotherapy research has historically been classified into two broad categories: efficacy and effectiveness research. Efficacy and effectiveness research represent unique yet complementary methods for conducting empirical studies on the effects of psychotherapy and have provided an abundance of evidence that psychotherapies of various kinds are effective treatments for a variety of psychological disorders. The primary differences between the two methods revolve around what is sometimes referred to as the “interpretability/generalizability” dilemma. Efficacy research, which seeks to answer the question, “Does the treatment work under well-controlled experimental conditions?” involves clinical trials of specific therapies. The goal of efficacy research is to maximize internal validity through stringent experimental control, thereby allowing researchers to more confidently attribute findings to treatment rather than to other factors that may have produced the results. In other words, efficacy research strives to ensure the interpretability of results. However, the stringent experimental control in this type of research is rarely, if ever, found in actual clinical practice, thereby limiting the generalizability of results. In fact, opponents of efficacy research and clinical trials have described it as a contextless method used to study context-rich participants and interventions. They argue that efficacy research is the wrong method for empirically validating psychotherapy as it is actually done, because it omits too many crucial elements of what is done in the field. Proponents, on the other hand, claim that efficacy research is the core method for placing treatments on a firm empirical foundation.

Effectiveness research, in contrast to efficacy research, attempts to answer the question, “Does the treatment work in practice?” The goal of effectiveness research is to maximize the external validity or generalizability of results. In other words, there is a high premium placed on studying treatments as they are routinely delivered by clinicians practicing in the field. Accordingly, effectiveness research is generally conducted in less controlled naturalistic or “real world” clinical settings, thereby bridging the gap between science and practice. While providing potentially valuable information to practicing clinicians, effectiveness research also has limitations. Due to the lack of stringent experimental control often present in these studies, results are often subject to many possible interpretations, and numerous replications with greater levels of experimental control are generally required to test alternative interpretations of results from such research. The differences in the objectives of efficacy and effectiveness research (i.e., stringent experimental control resulting in high internal validity allowing for interpretability of results versus less experimental control resulting in high external validity allowing for generalizability of results, respectively) are manifested in the conceptualization, design, and implementation of psychotherapy research studies. While it is sometimes difficult to categorize specific studies as being efficacy or effectiveness research because there is considerable variability and overlap in design features, these two methods typically differ in a variety of ways.

Selection of Participants

In efficacy research, several patient characteristics are often used to determine whether patients are included or excluded from a study. The rationale for establishing inclusion/exclusion criteria that guide selection of participants is based on the need to create a homogeneous group of patients, particularly with regard to diagnosis, that can subsequently be randomized to treatment and control conditions. For example, patients who meet criteria for a single diagnosed disorder are typically selected to participate, while patients with multiple disorders are typically excluded. Diagnostic interviews of potential study participants are conducted using standardized interview procedures with demonstrated reliability, such as the Structured Clinical Interview for Diagnosis (SCID), and the diagnosis is typically made in strict accordance with criteria established in the current edition of the Diagnostic and Statistical Manual of Mental Disorders. Furthermore, severity of impairment is often an inclusion/ exclusion criterion used in efficacy research. Patients must not only have a single disorder, but the severity of the impairment must fall within a specified range of scores on a particular standardized instrument. In other words, the patient's score on a standardized measure must not be too low, as this might cast doubt as to whether the patient's level of impairment warrants the diagnosis of the disorder/condition that is the focus of the study, but it must also not be too high so as to raise questions about the patient's suitability for participation (e.g., a patient who scores above a specified score on a standardized measure of depression may be experiencing significant suicidal ideation, making the patient unsuitable for the study for ethical reasons). Particular attention is often given to selecting “diagnostically pure” patients for participation in efficacy studies in order to ensure that the disorder of interest and associated symptoms, rather than some other condition or set of problems, are clearly identified. This, in turn, allows for target outcomes to be clearly operationalized (e.g., number of depressive symptoms, number of panic attacks). Age, presence of a specific physical illness, use of medications, concurrent treatment, and substance use are examples of other patient characteristics often used to exclude individuals from an efficacy study for the purpose of creating a homogeneous patient sample. Selecting a homogeneous group of patients, in addition to randomizing them to treatment and control conditions, makes it very difficult to attribute any observed differences between treatment and control groups to differences in patient characteristics.

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