RESUMEN
LAY ABSTRACT: Autistic children often experience higher levels of anxiety than their peers. It can be difficult to diagnose and treat anxiety disorders in autistic children, in part because of the high degree of variability in their underlying abilities and presentations. Some evidence suggests that autistic children with higher intelligence (as measured by intelligence quotient) experience higher levels of anxiety than autistic children with lower intelligence. However, the evidence is inconsistent, with other papers not finding a difference or finding higher levels of anxiety in autistic children with lower intelligence. In this article, we review existing literature to see whether autistic children with higher intelligence quotients have higher anxiety than autistic children with lower intelligence quotients. A systematic search of the literature was conducted which identified 49 papers on the topic. The methods of all the papers were reviewed using an objective quality assessment framework. When combining the data statistically, there was evidence that autistic children with higher intelligence quotients are more anxious than autistic children with lower intelligence quotients. The quality review raised common weaknesses across studies. Most importantly, few studies used measures of anxiety that have been shown to be valid for children with very low intelligence quotients. Similarly, many studies used measures of anxiety that have not been shown to be valid for autistic children. These factors are important because autistic children and those with low intelligence quotient may experience or understand anxiety differently. Future research should use fully validated measures to test whether high intelligence quotient is associated with high levels of anxiety in autistic children.