In the mental health literature, the terms "heavy users" or "high utilizers" have been coined to describe a relatively small group of people with chronic mental illness, with excess use of inpatient psychiatric services. Although these terms are used both nationally and internationally, there is no consensus on how they are defined. For example, in Switzerland, they are used by the Swiss Health Observatory (Obsan) and the Federal Office of Public Health. Previous research suggests that even though only 10% to 30% of all inpatients qualify as "heavy users", their use of the healthcare system's resources is well above average. In German-speaking countries, there are currently only a few scientific studies on this group of patients, especially on the question of which offers are best suited to better integrate existing models of care, and how to make them more effective. Due to the separate enumeration of outpatient and inpatient care in Switzerland (as in many other countries), integrated models of care that are particularly needed for this group of patients are currently lacking. This can result in costly under- and incorrect treatment with more frequent discontinuations. In addition, apart from the treatment of medical issues, other aspects often play an important role in the care of chronically ill patients, such as socio-economic difficulties (e.g. in the areas of work and housing or financial problems). Therefore, in the recently completed National Research Program (NRP) 74 "Healthcare" of the Swiss National Science Foundation, the numerous interfaces between care settings were identified as a central field of action, which is a particularly the case in patients with chronic illnesses: "In the highly specialized, decentralized health care system in Switzerland, coordination between multiple medical and non-medical services is difficult."

INTUK (Integrated care after repeated psychiatric hospital stays) represents a new interprofessional and integrated care program at Klinik Zugersee, which aims to bridge such interfaces and improve the treatment of people with chronically recurrent mental illness. A team consisting of a senior physician, nurse, social worker, and peer will deliver person-centered care tailored to individual needs in these mostly complex care situations. Contact is initiated with the affected patients during their inpatient stay to build relationships and increase motivation for subsequent, individually planned treatment and care. For example, round-table discussions can take place with the specialists and community-based providers involved in the follow-up treatment before the patient is discharged. After discharge, the same team continues to provide support and coordinate access to outpatient and semi-inpatient treatment, counselling and self-help services. In the case of social difficulties, social work coaching or accompaniment to offices and social institutions takes place will be provided. Another service is the joint drafting of a psychiatric living will to determine consent and rejection for future psychiatric treatments. Wherever possible, close others and the wider social environment are also included in consultation with the patient.