Cross-sectional developmental trajectories in the adaptive functioning of children and adolescents with Down syndrome

Background: Persons with Down syndrome (DS) reveal adaptive functioning (AF) difficulties. Studies on AF in DS have focused mainly on describing the profile (i.e., strengths in socialization, and weaknesses in communication), while less is known about age-related differences. This study aimed to elucidate how AF changes with age in children and adolescents with DS, taking a cross-sectional developmental trajectory approach. Moreover, the contribution of both chronological age (CA) and mental age (MA) on AF development was explored.Method: This study involved 115 children and adolescents (between 3 and 16 years old) with DS. Parents were interviewed about their children's AF on communication, daily living and social-ization skills. Children and adolescents with DS were assessed on their developmental level.Results: While participants' standard scores on AF decreased linearly over time, their age-equivalent scores increased with linear or segmented patterns, depending on the skill consid-ered. CA and MA were related to daily living skills and socialization to much the same degree, while MA correlated more strongly than CA with communication.Conclusion: This study contributes to the understanding of how AF develops in children and ad-olescents with DS, showing that CA and MA both contribute to shaping the skills involved.