Good health partly determines the quality of your life and to what extent you are able to participate in society. People with profound intellectual and multiple disabilities (PIMD) often have multiple health issues, which is called multimorbidity. The number of health issues usually increases when people get older. There is a growing awareness of the health issues that occur in children and adults with PIMD, but very little is known about whether multimorbidity also occurs, how it arises and develops, and whether any patterns can be discerned in this area. This PhD study focuses on developing knowledge on this topic to ensure that the screening for health issues in people with PIMD is more targeted and that treatment or preventive treatment is started in time.