Abstract
People with autism spectrum disorder (ASD) and non-spectrum developmental delays frequently exhibit maladaptive behaviors throughout the lifespan, which can have pervasive effects on quality of life. Maladaptive behaviors have been shown to change over time as a function of various individual-level factors (e.g., cognitive ability), yet research is primarily limited to parent-reported measures. To expand upon this work, the present study aimed to examine trajectories of teacher- and parent-reported maladaptive behaviors (i.e., hyperactivity, irritability, social withdrawal) and to test whether individual-level predictors (e.g., autism features, verbal intelligence quotient) and school-related predictors (e.g., teacher type, student-adult ratio, personal aide, school type) impact these trajectories among 165 individuals with ASD or non-spectrum delays from ages 9 to 18. Multilevel models revealed that, according to both teacher and parent report, participants showed the greatest improvement in hyperactivity, less but still notable improvement in irritability, and stable levels of social withdrawal over time. Higher verbal ability and fewer ASD features, in addition to mainstream school placement, emerged as important individual- and school-related differences associated with fewer maladaptive behaviors over time. The multi-informant perspective and longitudinal design provide novel insight into the manifestations of these maladaptive behaviors across different contexts and across time. Findings highlight the consistency of teacher- and parent-reported trajectories over time and further emphasize the importance of targeting maladaptive behaviors using a multisystem intervention approach in both school and home contexts.