[What is psychotherapy? An interdisciplinary proposal for a definition].

The definition of psychotherapy has wide-ranging implications for research and clinical care as well as for legal issues, as set out in the German psychotherapy guidelines. It can determine which services are covered by health insurance and who is authorized to provide the services. In light of the ongoing debate regarding the evidence base of psychotherapy, a group of experts from various professional disciplines with different theoretical and methodological backgrounds and focusing on different age groups, has worked together with individuals with personal experience of psychotherapy and young clinicians to engage in a discussion process aimed at arriving at a contemporary definition of psychotherapy. This incorporates the current body of empirical evidence, enables innovative developments towards a transtheoretical, transdiagnostic and personalized psychotherapy and places the needs of patients at the center. Our literature review leads to a definition of psychotherapy comprising four aspects: treatment modality or "tools" (treatment modality)? How does the treatment work (proposed mechanisms of action, assumptions about causal and evidence-based processes)? Who receives psychotherapy (target group)? Who provides psychotherapy (provider)? Our proposed definition is not bound to specific treatment theories and orientations but aims to promote the evidence-based provision of psychotherapy within the German healthcare system and in accordance with the legal framework.