[What is science-based psychotherapy? On the discussion of guidelines for psychotherapy research].

The scientific nature of psychotherapy can be defined by two partially interrelated criteria: validity of the theory underlying a therapy and efficacy or effectiveness of a therapy. To enhance the scientific basis of a psychotherapeutic approach, research is needed on therapeutic objectives, principles, and processes, measuring methods, process-outcome relationships, and efficacy and effectiveness of therapies. Determination of efficacy requires randomized clinical trials (RCT). The scientific basis must be seen as the continuous development of a psychotherapeutic approach. In contrast, the question of whether a psychotherapeutic approach is well established is dichotomous. In addition to scientific criteria, those deriving from mental health policy and economics are also important. This paper presents various approaches to ascertaining efficacy. According to the criteria of the American Psychological Association Task Force, to be "well-established," treatments for specific disorders must be shown efficacious in at least two independent randomized clinical trials. Although comparability is limited, we propose that psychotherapeutic research be conceptualized into phases, as in pharmacotherapeutic research.