Differences in anxiety (P = 0.69) and grit (P = 0.46) were not significant when compared to sibling controls; however, 58% (7/12) of KCNJ11-NDM participants and 40% (4/10) of sibling controls had scores indicating an anxiety disorder by either self- or parent-report.<h4>Conclusions</h4>Our results agree with previous studies suggesting significant difficulties with social functioning in KCNJ11-NDM, with 7/10 participants having scores suggestive of ASD, strongly reinforcing the need for early neurodevelopmental screening to allow for prompt support. This evidence concerns the gene KCNJ11 and anxiety disorder.