Background and AimsAnxiety and depression symptoms are common among autistic youth, yet little is known about the pattern and relationship of their trajectories from childhood into adolescence, a period of increasing social and academic demands.MethodsThis study used parallel process latent growth curve models to examine joint trajectories, including initial levels and rate of change in caregiver-reported depression and anxiety symptoms across age 7–16 within an inception cohort of autistic youth with varied communication abilities. We also examined autistic traits, sex assigned at birth, emotional reactivity and communication ability as potential predictors. Child anxiety and depression symptoms were estimated from Child Behavior Checklist Anxiety and Affective Problems subscales, completed by caregivers approximately annually.ResultsWhereas anxiety symptoms were relatively stable from childhood into adolescence, depression symptoms increased on average; significant heterogeneity of individual trajectories underlaid these overall trends. Findings indicated cross-sectional and longitudinal co-occurrence of anxiety and depression symptoms. Greater autistic traits and emotional reactivity correlated with greater initial anxiety and depression symptoms, but not their trajectories. Stronger communication ability correlated with more initial anxiety, but decreasing anxiety symptoms over time.ConclusionsFindings indicate group-level changes in depression symptoms and synchronous evolution of anxiety and depression symptoms in autistic youth across childhood and adolescence. This indicates the importance of joint monitoring of anxiety and depression symptoms in this period, with changes being potentially informative for early detection and intervention. Considering how anxiety symptom presentation may evolve across development may be a helpful next step to identifying at-risk subgroups.

