Anxiety and intellectual functioning in autistic children: A systematic review and meta-analysis
Authors: Mingins Jessica E , Tarver Joanne , Waite Jane , Jones Chris , Surtees Andrew DR 
Published: November 2020

Autistic children experience higher levels of anxiety than their peers. Making appropriate diagnoses of anxiety disorders and providing effective treatment for these children is particularly difficult. Inconsistent evidence suggests that levels of anxiety in autistic children are related to intellectual functioning. We provide the first meta-analysis of this evidence. A systematic search identified 49 papers for review. These papers included measures of anxiety and intelligence quotient in 18,430 autistic children. Studies employing correlations showed evidence of a significant relationship between intelligence quotient and anxiety in autistic children: children with higher intelligence quotient scored higher on measures of anxiety. Studies directly comparing groups of autistic children with and without intellectual disability also supported this conclusion. Most studies employing other designs also supported this finding. Employing a quality assessment framework identified common threats to validity. Many studies used measures of anxiety that were not validated across the samples they measure. This was most notable for those autistic children with an intellectual disability. It is vital that future research determines whether the identified relationship between intelligence quotient and anxiety reflects something important in the mechanism for anxiety in autistic children, or quantifies the lack of sensitivity of our measures of anxiety across different groups. 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.