The purpose of this study is to investigate:

1) the implementation and 2) the effects of an outpatient program for patients with complex multimorbidity. The investigators intend to integrate care from various health professionals across medical specialties and sectors, promote person-centered care, and ensure a holistic approach. Specifically, the investigators have redesigned the existing clinic, the Clinic for Multimorbidity, which has been operational since 2012 without any protocol-based evaluation. The new version introduces differentiated care options based on general practitioners needs for support.

Multimorbidity, defined as the presence of two or more chronic diseases in an individual, poses a significant challenge for healthcare systems globally. There is an urgent need for targeted interventions for those with high complexity, such as due to interacting diseases and polypharmacy, particularly in light of an aging population, where on-fourth has multimorbid. Although the care for individuals with multimorbidity often may be perceived as fragmented, there is limited evidence on how to best organize the care. Effective, evidence-based strategies to ensure integration are lacking.

The population will consist of adults with complex multimorbidity from the Central Denmark Region, referred to the Clinic for Multimorbidity from general practice. Using a stepped wedge randomized controlled design, the project will encompass two studies.

1. The implementation study will be based on implementation outcomes by Proctor et al: acceptability, adoption, appropriateness, feasibility, fidelity, and penetration. Data will be collected through interviews with patients and general practitioners, as well as measurements related to referral practices, costs, and feasibility.
2. The effectiveness study will include outcome measures such as questionnaire-based patient experiences regarding health-related quality of life, treatment burden, depression, and anxiety. Additionally, the investigators will assess effects on inappropriate medication, symptoms, mortality, treatment continuity, healthcare utilization, and the initiation of health-promoting initiatives.

The investigators anticipate demonstrating that multimorbid patients will benefit from an interdisciplinary, cross-sector collaborative model. Furthermore, the investigators expect that this new organization will support general practitioners, municipalities, and hospitals in their management of these patients, addressing differentiated treatment needs in accordance with the recommendations of the Danish Health Structure Commission.

Inclusion Criteria:

• Aged18 years or older
• Multimorbidity: = 2 chronic conditions (minimum 6 months' duration per condition)
• Polypharmacy (= 5 medications)
• Complexity: Complex multimorbidity refers to the patient suffering from multiple concurrent, chronic diseases/conditions creating additional challenges. Complexity can be of physical, mental, social character and due to medication, high treatment burden, frailty, frequent healthcare visits or a special need for joint healthcare collaboration.

Exclusion criteria:

Diagnostically unresolved conditions and patients whose primary issues require focused management of chronic pain, psychiatric disorders, alcohol misuse, and other addiction-related challenges.