REVIEW ARTICLE A Scoping Review of Anxiety in Young Children with Autism Spectrum Disorder Roma A. Vasa , Amy Keefer , Rachel G. McDonald, Michelle C. Hunsche, and Connor M. Kerns Research on anxiety in children and adolescents with autism spectrum disorder (ASD) has burgeoned in the past 15 years. Most of the research has focused on school-age children, ages 6 to 18 years. Yet, recent studies suggest that anxiety can emerge in young children, under 6 years, with ASD. This scoping review synthesized the literature on anxiety in young children with ASD. Three domains of anxiety research were reviewed: (a) prevalence/severity, phenomenology, and course; (b) correlates; and (c) treatment. Four online databases were searched from the start of the database until March 2020. Keywords pertaining to anxiety, autism, and young children were entered. The search identified 44 articles for inclusion. These studies varied with respect to sample source, informants, and measures to assess anxiety. The overall prevalence of anxiety ranged from 1.6 to 62%. Sixteen of 17 studies found that young children with ASD had higher levels of anxiety compared to various control groups. A variety of DSM anxiety symptoms and disorders were present in young children with the most common symptoms being specific, social, and generalized fears. Correlates of anxiety included sensory over-responsivity, sleep disturbance, aggression/defiance, and attention deficit/hyperactivity disorder. Three cognitive behavioral treatment studies for anxiety and one developmental intervention targeting ASD symptoms showed promise in reducing anxiety. Findings indicate an early emergence of anxiety in some children with ASD. Further research on the measurement, pathophysiology, and treatment of anxiety in early childhood is critical to improving out- comes in children with ASD. Autism Res 2020, 00: 1–20. © 2020 International Society for Autism Research and Wiley Periodicals LLC. Lay summary: This scoping review synthesizes the literature on anxiety in young children with autism spectrum disorder (ASD). Results indicate that children with ASD have higher levels of anxiety than children without ASD. Potential factors that could be contributing to anxiety include sensory, sleep, and behavioral problems. Preliminary studies show that anx- iety can improve with cognitive behavioral treatment. These findings suggest that research on anxiety in young children with ASD should be prioritized to improve mental health outcomes. Keywords: anxiety; autism; review; young children Introduction Anxiety disorders are among the most prevalent and dis- abling comorbidities associated with autism spectrum dis- order (ASD) [Simonoff et al., 2008]. Approximately 40% of school-age children with ASD (i.e., 6–18 years) suffer from an anxiety disorder, which is nearly double the prevalence of anxiety in children without ASD [Beesdo, Knappe, & Pine, 2009; Simonoff et al., 2008]. Research indicates many similarities, but also some variations in the phenomenology of anxiety disorders in children with versus without ASD [Kerns & Kendall, 2012]. As in typi- cally developing (TD) youth, research suggests that anxi- ety symptoms in children worsen with age and have a negative impact on the academic, social, and adaptive functioning of children with ASD [Chang, Quan, & Wood, 2012; Drahota, Sterling, Hwang, & Wood, 2013; Gotham et al., 2013; Kim, Szatmari, Bryson, Streiner, & Wilson, 2000]. The heightened prevalence and impact of anxiety on major life domains for children with ASD sug- gests a pressing need to improve anxiety detection and treatment in this population. Considerable evidence supports the occurrence of anxi- ety disorders in TD young children, and the association of this early life condition with psychiatric disorders in mid- dle school and adolescence [Finsaas, Bufferd, Dougherty, Carlson, & Klein, 2018; Whalen, Sylvester, & Luby, 2017]. Furthermore, evidence suggests that treating anxiety From the Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, Maryland (R.A.V., A.K., R.G.M.); Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland (R.A.V., A.K.); Department of Psychology, University of British Columbia, Vancouver, British Columbia, Canada (M.C.H., C.M.K.) Received May 14, 2020; accepted for publication August 27, 2020 Address for correspondence and reprints: Roma A. Vasa, Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, MD 21211. E-mail: vasa@kennedykrieger.org Published online 00 Month 2020 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/aur.2395 © 2020 International Society for Autism Research and Wiley Periodicals LLC. INSAR Autism Research 000: 1–20, 2020 1