Method: The KOSMOS intervention combines the most effective research results to improve staff competence, and patients' mental health, safety, QoL, and to reduce psychotropic drug use and costs. The efficacy testing of KOSMOS includes systematic literature review, a pilot study, a 9-month randomized control trial (RCT), and a dissemination plan. Data collection will take place at baseline, months 4, and 9. The intervention entails provision of staff training, study guidelines and manuals. NHs will be randomized to either KOSMOS or current best practice. We will include 38 NH long-term-care (LTC) wards (normally just one ward per NH) in Bergen, Stavanger, Oslo/Bærum, Sarpsborg and Sogn and Fjordane. In total 310 patients ≥65 years will be recruited from these wards