Selective mutism (SM), considered an early-onset variant of social anxiety disorder (SAD), shares features of impaired social interaction and communication with autism spectrum disorders (ASDs) that suggest a possible shared pathophysiology. We examined the association of a susceptibility gene, contactin-associated protein-like 2 (CNTNAP2), for ASDs and specific language impairment (SLI) with SM and social anxiety-related traits.
Sample 1 subjects were 99 nuclear families including 106 children with SM. Sample 2 subjects were young adults who completed measures of social interactional anxiety (SIAS; N = 1028) and childhood behavioral inhibition (RSRI; N = 920). Five SNPs in CNTNAP2 (including rs7794745 and rs2710102, previously associated with ASDs) were genotyped.
FBAT analyses revealed nominal significance (p = 0.018) for association of SM with rs2710102 which, with rs6944808, was part of a common haplotype associated with SM (permutation p = 0.022). Adjusting for sex and ancestral proportion, each copy of the rs2710102*a risk allele in the young adults was associated with increased odds of being >1SD above the mean on the SIAS (OR = 1.33, p = 0.015) and RSRI (OR = 1.40, p = 0.010).
Although association was found with rs2710102, the risk allele (“a”) for the traits studied here is the non-risk allele for ASD and SLI (“g”). These findings suggest a partially shared etiology between ASDs and SM, but raise additional questions about specific aspects of these syndromes (i.e., language impairment and/or social anxiety) potentially influenced by CNTNAP2 and mechanism(s) by which these influences may be conveyed.