Kampo medicine, a traditional medicine of Japan, was used in psychiatric practice in the latter half of the 18th century (the Edo era). Pharmacotherapy using Kampo formulas was carried out before the arrival of therapeutic drugs from the Western world. From that time to the present, the core of Kampo therapy has been "zuisho-therapy", in which treatment proceeds according to the Kampo medical diagnosis ("sho"). In recent years, "evidence-based medicine (EBM)" has also been used in a similar way to modern medicines. In the present study, we discuss the future prospects and issues of kampo medicine in psychiatry based on the concepts of "vertical evidence" and "horizontal evidence". Currently, most Kampo formulas prescribed in psychiatric clinics are those based on EBM (horizontal evidence) such as yokukansan for behavioral and psychological symptoms of dementia (BPSD). However, a minority of cases are prescribed a Kampo formula based on zuisho-therapy (vertical evidence). Thus, Kampo therapy that makes full use of horizontal evidence will probably continue to be performed in the future. Herein, we advocate for the use of vertical evidence of zuisho-therapy that has been cultivated over a long time. Previous studies suggest that yokukansan is effective for BPSD; however, for some cases who do not respond well to yokukansan, orengedokuto or saikokaryukotsuboreito may be effective. Further studies are needed to investigate combining horizontal evidence (modern medical evidence) and vertical evidence (zuisho-therapy).
 Author's abstract