Development of a family-centered intervention to support self-determination in adolescents and young adults with intellectual disability in home environments: Protocol for a multistage mixed methods design

qualitative study involving semi-structured interviews and observations with families of young children with disabilities to examine how the home environment influenced the strategies they used to support their children's self-determination.The authors identified several strategies used by these families, such as encouraging children to choose what they want to eat, creating spaces for play and interaction with others, supporting independent movement around the house, teaching goal achievement during play with toys, and providing opportunities for children to control their personal space and privacy [19,22].Another notable gap identified in Dean et al.'s [31] review was the scarcity of interventions focused on family support and self-determination, with only three studies reporting such interventions.The scarcity of interventions, specifically in Spain, was also highlighted in a previous study by Arellano and Peralta [18] that examined Spanish parents' attitudes towards young children with intellectual disability. Study purpose and research questionsThis paper reports the protocol for a multistage mixed methods study.In order to address the gaps in the body of research discussed above, the purpose of this mixed methods study is to determine how self-determination develops and is supported in home environments in adolescents and young adults with intellectual disability and a mild or moderate level of support, with the aim of developing an intervention to promote self-determination in these environments.The study is based on a family-centered approach, thus considering the family as a unit of intervention and as the key factor in implementing the study.This approach relies on collaboration between families and professionals to achieve the design of the intervention.We aim to answer the following research questions:Research question 1: How do families of adolescents and young adults with intellectual disability support the self-determination of these individuals in their home environments in Spain?Research question 2: What context-sensitive strategies and practical actions are identified by professionals, adolescents and young adults with intellectual disability, and their families as relevant and feasible to support the self-determination of adolescents and young adults with this disability in home environments in Spain?Research question 3: What are the main elements of a desirable context-sensitive intervention to support the self-determination of adolescents and young adults with intellectual disability in their home environments in Spain?Research question 4: What strategies should be used to implement this intervention? Theoretical frameworkThis study is based on the Causal Agency Theory, developed by Shogren et al. [3] to explain how people (with and without disabilities) become self-determined in the course of their lives.Drawing on the principles of strengths-based approaches to disability, positive psychology, and the social-ecological model of disability, which emphasizes the interaction between individuals and their environment, this theory constitutes a valuable framework for explaining how individuals, at different stages of their life, "define the actions and beliefs necessary to engage in self-caused, autonomous action that addresses basic psychological needs" [33].According to this theory, self-determined individuals are causal agents who "act in service to freely chosen goals that propel action" [17].This theory has three main elements: volitional actions, agentic actions, and action-control beliefs (i.e., to decide, to act and to believe).Specific skills associated with volitional action include choice-making, decision-making, goal setting, problem-solving, and planning; those associated with agentic action include self-management, goal-attainment, problem-solving, and self-advocacy; and those related to action-control beliefs include self-awareness and self-knowledge. Methods and analysis Study designUsing a multistage mixed methods design [34,35], this study will include three sequential phases: Phase 1, a grounded theory study involving the families of individuals with intellectual disability, and addressing research question 1; Phase 2,