Thiele-Swift, Henry Noah2024-06-132024-06-132023https://hdl.handle.net/2440/141247This item is only available electronically.Background: The prevalence of anxiety disorders and symptoms in young children and adolescents (<18 years) diagnosed with Autism Spectrum Disorder (ASD) is obfuscated by a reliance on self-reported ASD traits and treatment samples. Aim: To update current prevalence estimates of anxiety prevalence among ASD youth and examine the role of methodological and sample moderators. Methods: The Embase, PubMed, and PsycINFO databases were searched (1970 - August 2023). Included studies were critically appraised using the Joanna Briggs Institute (JBI) tool and prevalence estimates meta-analysed with random-effects modelling. Moderator analyses focused on IQ, publication date, anxiety measurement, age, and gender. Results: Fifteen studies, comprising a pooled sample of 4,459 ASD youth, who were primarily male (84%), were included. The overall prevalence of anxiety disorders or symptoms was 30% (95% Cl 24% to 37%). Estimates based on diagnostic tools (19%, Cl: 7% to 40%) and self-reported symptoms (33%, CI: 25% to 40%) were equally high (Qg (1) = 1.633, p = 20). Specific phobia (41%) was the most common anxiety disorder. IQ (R = .39, p =.004) and male gender (QB (1) = 35.02, p < 01) were also identified as significant moderators. Conclusion: Anxiety comorbidities affect 1 in 3 youth living with ASD. This rate is notably lower than previous meta-analyses that have used less stringent inclusion criteria relating to the assessment of ASD or anxiety (range 39.6% to 42%). The findings highlight the importance of screening for anxiety in this population. Protocol registered on Open Science Framework (https://osf.io/7mtca/). Keywords: children, ASD, anxiety disorders, prevalenceHonours; PsychologyThesis