Participation is often defined as taking part and being included in different areas of life. Leisure represents an important area of life for all people. People with disabilities have the right to experience leisure time in a self-determined manner. They have the right to participate in leisure activities on an equal basis with others.
Participation is defined as ‘being involved in life situations’ 
. Being involved is determined by the limitations of the body’s structures and functions, as well as contextual factors, and manifests itself in the performance of activities, such as communicating, learning, and being mobile. These activities can be assigned to different domains of life, such as self-care, home life, community, and social and civic life. In the domain of ‘community, social and civic life’, participation in leisure activities is defined as consisting of play, sports, culture, crafts, hobbies, and social activities. Dijkers 
extended the concept of participation. He describes participation as the extent or degree to which people take part in various activities and fulfill specific roles; therefore, participation can be objectively operationalized as active engagement, which can be quantitatively observed by measuring the duration and frequency. Qualitatively, leisure time participation can be assessed through subjective perceptions of leisure time. As people with severe or profound intellectual disabilities often communicate nonverbally using idiosyncratic symbols 
, their leisure participation can be observed through expressions such as mimicking and gesturing emotions, including pleasure, happiness, and/or enjoyment 
. Whilst participation is important in all areas of life, this research focuses on participation in leisure activities of people with intellectual disabilities (ID) and the influencing factors of various activities.
2. Leisure as an Important Domain of Life
Leisure time has become increasingly important in the course of the post-industrial reduction in working hours 
. In addition to the quantitative increase in free time, social developments in Western societies have led to a change in the way it is treated. While free time has long been viewed as ‘leftover’ time distinct from working time 
, qualitative characteristics, such as self-determined freedom to shape one’s own life, are now seen as hallmarks of this period of time 
. Thus, in the discourse of leisure research, different concepts of leisure exist, which can be shaped by different disciplines. In summary, leisure can be viewed in various ways:
As activity—some activities involve planning, the use of facilities or equipment, and the involvement of other people. Others are much more spontaneous.
As time—leisure takes place in ‘non-obligated time’, in other words, those occasions when we are free of responsibilities and the demands of others.
As a state of mind—when we feel free to choose our activity to please ourselves, without external pressure or rewards 
Leisure time plays an important role in the lives of all people. Especially in the course of identity development in adolescence, leisure time represents an area of life in which adolescents can learn more about themselves and define their character apart from adults 
. Free time provides the space and freedom of action to try new activities, demonstrate skills, connect with others, and stand up for and express oneself. Numerous studies demonstrate the qualitative value of free time in the lives of people (e.g., 
). Social roles, values, and norms can be tried and tested in leisure. Leisure beckons opportunities to experiment with these qualities and to test and develop facets of oneself. Engaging in new activities during leisure time offers opportunities to discover new interests, pursue one’s intrinsic motivation to engage in activities, and form relationships with others. Thus, social–emotional development is strengthened, and empathy, self-determination, self-efficacy, and autonomy are promoted 
. However, Larson 
points out that autonomy is not unconditional. For example, there are many people who have only limited opportunities to develop their decision-making competence due to influencing factors, such as time determined by others, limited options for action, little time, and/or a high level of dependence on others. Leisure activities in particular are based on the principle of voluntariness. They are therefore well suited for learning and consolidating autonomy and self-determination while taking the social context into account. Participation in social leisure activities can promote community participation and inclusion. In this regard, Doistua et al. 
distinguished between guided and self-organized leisure activities. When people have the opportunity to organize their leisure time according to their wishes in an intrinsically motivated way, they not only experience leisure time positively, but their satisfaction also increases. Leisure time has a great impact on the quality of life 
. Thus, leisure participation affects emotional, social, mental, and physical well-being. Leisure represents an area of life that affects all people. People with disabilities also have leisure needs, just like any other person. To promote inclusive participation in leisure, contextual factors are needed that enable the person to find, access, and benefit from leisure opportunities. Aitchison 
considers the study of disability and leisure to be important to make leisure inclusive.
3. Leisure Participation of Individuals with Intellectual Disabilities
Research indicates that children and adolescents with a wide range of intellectual disabilities experience limitations in leisure participation within their community environments 
. Melbøe and Ytterhus 
investigated what types of activities adolescents with intellectual disabilities participate in during their free time. The study shows that youth with intellectual disabilities have the same preferences and desires for leisure activities as their peers without disabilities. However, a closer look reveals that youth with intellectual disabilities lack access to institutionally organized leisure activities, thus limiting their ability to express their preferences, which negatively impacts their well-being 
. Buttimer and Tierney 
suggested in their study that the leisure activities of young people with intellectual disabilities are predominantly passive and medial in nature. This type of leisure activity is often carried out alone within their home. In addition, the parents of children with disabilities cite a lack of friendships, the feeling of ‘not being welcome’, and a lack of leisure-oriented skills as the most frequent barriers to leisure activities. Leisure time increasingly takes place in the individual private sphere, and social participation and the choice of leisure activities seem to be limited. However, a study by Eratay 
shows that leisure activities in particular offer opportunities for social interaction, which in turn can have a positive effect on the development of social skills and a reduction in behavioral problems in young people with intellectual disabilities. In addition to social action, self-determination and the subjective attribution of meaning in the performance of leisure activities are recognized as important elements of leisure participation 
. Thus, the environment represents an important determinant when it comes to participation 
. For individuals to be able to act in a self-determined manner, they need choices in their environment that they can intentionally decide on based on their needs and competencies. Eldeniz and Cay 
examined school-based leisure support for students with intellectual disabilities. They found that participation in leisure activities increases when students are allowed to choose the leisure activity on their own. If the teacher determines the activity, the active participation of the students is lower. Dahan-Oliel, Shikako-Thomas, and Majnemer 
conducted a systematic review of the relationship between leisure participation and quality of life in children with neurodevelopmental disorders. They were able to show that active physical leisure participation is related to increased physical and emotional well-being, that successful leisure participation with others results in increased social well-being and increased self-efficacy, and that exercising leisure preferences is related to well-being and individual satisfaction. The promotion of participation in leisure activities by adolescents, therefore, seems to be an important concern in the context of quality of life. Studies on leisure participation of adults with intellectual disabilities also show similar results. Badia et al. 
investigated the relationship between leisure activities and the quality of life of people with developmental and intellectual disabilities. They found positive correlations between the expression and exercise of leisure preferences and individual well-being. Participants with disabilities who perceive limitations in their participation in leisure activities show lower levels of emotional and physical well-being