Abstract
Given high rates of co-occurring conditions in youth and adults with autism spectrum disorder (ASD), it is critical to examine the developmental trajectories of these symptoms of psychopathology. Using data from a cohort of participants (n = 194), most of whom were first assessed for ASD in very early childhood, we investigated the trajectories of co-occurring depressive, anxiety, and attention-deficit hyperactivity disorder (ADHD) symptoms from late childhood to adulthood. Additionally, childhood predictors and adult outcomes associated with these symptom trajectories were examined. Using group-based trajectory modeling, we found two distinct classes of individuals exhibiting each of these co-occurring symptom patterns: one class exhibited fairly low symptoms across time, and one class with elevated symptoms with varied fluctuation across time (ADHD symptoms starting high but decreasing, anxiety symptoms high and stable, and depressive symptoms fluctuating but peaking at clinically significant levels in young adulthood). All high trajectory classes were associated with age 9 adaptive skills; verbal IQ predicted higher anxiety and depressive symptom classes. After accounting for verbal IQ, all high symptom trajectory classes were negative predictors of objective adult outcomes. These findings call for wide-ranging considerations of the needs of individuals across ability levels, autism symptoms, and behavioral and emotional challenges.