Over half of adolescents with Down syndrome (DS) have difficulty being understood by others which negatively impacts their engagement in daily life activities that require communication (i.e., communicative participation). Restrictions in communicative participation are not trivial and lead to un- and underemployment and loneliness which, in turn, lead to poor mental and physical health outcomes. Despite the urgent need, interventions to improve speech production in adolescents with DS are rare. Thus, speech-language pathologists use treatments that are designed for adults, are not specific to the underlying impairment in DS, and do not consider the unique psychosocial issues faced by adolescents. The long-term goal of this line of research is to bring a precision medicine approach to the development of theoretically-driven, evidence-based, participation- focused interventions for adolescents with DS. As a first step, we will construct deep phenotypes of communicative participation for adolescents with DS. Current intervention approaches focus exclusively on the underlying impairment while ignoring both the adolescent’s perspective and the societal structures that contribute to their disability. A key innovation of this proposal is the shift away from treating communicative participation solely as an impairment-level issue and toward a model of communicative participation that encompasses a broader view of functioning. To do so, we will employ the conceptual framework detailed in Baylor (Co-I) and Darling-White (PI; 2020) that models communicative participation as a biopsychosocial construct comprised of the following elements: communication skills (e.g., the underlying impairment), personal perspectives (e.g., preferences, coping), and communication environment (e.g., physical, social). Each element contributes to restrictions in communicative participation and warrants full consideration in intervention design and implementation. A critical barrier to the development of participation-focused interventions for adolescents with DS is the lack of empirical information regarding these elements, leaving us with a limited ability to identify intervention targets, measure progress, and facilitate lasting change. The first specific aim of this proposal is to construct impairment-level speech production profiles for adolescents with DS. The second specific aim is to investigate how personal perspectives and communication environment alter communicative participation for adolescents with DS. The third specific aim is to develop a mechanistic model of communicative participation for adolescents with DS. The expected outcome of this proposal is the deep phenotyping of communicative participation for adolescents with DS. By applying a precision medicine approach within a biopsychosocial framework, this proposal will lay the foundation for the creation of intervention that centers the patient perspective, addresses the underlying impairment based on comprehe...