The significance of the principal diagnosis in Germany's new payment system for inpatient treatment of mental disorders

In 2013 Germany implemented a new payment system for the inpatient treatment of mental disorders. Besides perpetuating a per-diem payment, the payment system sets up a classification system that groups cases with comparable costs per diem. The first release of the system reveals the principal diagnosis to be the main grouping variable. Especially in psychosomatic and psychotherapy this approach seems to be at least questionable. Because of the insufficiently precise definition of the assignment of the principal diagnosis in the coding standards - and therefore the expected conflicts between clinics and health insurance funds - this paper discusses the difficulties involved in defining the principal diagnosis. It also formulates recommendations of how the principal diagnosis should be assigned.