Identifying Genetic and Behavioral Correlates of Sensory Issues in Autism Spectrum Disorders

Background:

Sensory modulation characteristics are now part of the DSM-5 Autism Spectrum (ASD) classification and defined as: “hyper- or hypo-reactivity to sensory input or unusual interest in sensory aspects of the environment” (DSM-5, p.50). Research regarding sensory modulation suggests that upwards of 80% of all individuals on the autism spectrum report some degree of hyper- or hypo-sensory sensitivity. However, there is almost no data on the possible genetic underpinnings that might be involved in sensory sensitivities and only minimal data reported on family members of individuals with ASD.

Objectives: We hypothesize that in addition to sensory modulations issues that affect individuals with ASD, nuclear family members might also present with sensory sensitivity characteristics but to a lesser degree. These behaviors could be considered a characteristic of the Broad Autism Phenotype (BAP) and thus, might be used as a behavioral phenotype in family genetics studies.

Methods: One hundred twenty-seven (127) probands with ASD and 316 of their nuclear family members participated in a family genetics study. All probands received the ADI-R and all family members, including the probands, received the Social Responsiveness Scale (SRS and SRS-2). We used questions 20 (related to hyposensitivity/sensory seeking) and 42 (related to hypersensitivity) to categorize all family members as affected for sensory modulation issues. For ASD probands, we also included ADI questions 71, 72, & 73 to calculate affection rates for sensory issues. We examined the rates of sensory issues in all family members and categorized each member as affected or unaffected for a preliminary linkage analysis.

Results:

Hyposensitivity-Based on a combination of SRS and ADI-R data, parents reported that 86.9% of ASD probands had hyposensitivity issues. Based on SRS data, 16% of fathers, 14% of mothers, and 17% of unaffected siblings (US) also reported hyposensitivity. Group differences were significant when ASD probands were included [X² (3, N=443), 261.277, p<.001] but not significant for family member status or sex when probands were excluded from the analysis.

Hypersensitivity- Based on a combination of SRS and ADI-R data, parents reported that 87.9% of ASD probands had hypersensitivity issues. Based on the SRS data regarding hypersensitivity, 26% of fathers, 17% of mothers, and 26% of US reported hypersensitivity. Group differences were significant when ASD probands were included [X² (3, N=443) 206.570, p <.001] but not significant for family member status or sex when ASD probands were excluded from the analysis.

Preliminary genetic linkage analysis- Linkage analysis was performed on both variables. We observed evidence of linkage (90% posterior probability) for the hypersensitivity variable on Chromosome 6 while there was no evidence of linkage observed for hyposensitivity.

Conclusions:

As predicted, ASD probands showed high rates of hypo- and hyper- sensitivity supporting the inclusion of sensory modulation in DSM-5 ASD diagnosis. Preliminary exploration of rates in unaffected family members also show some degree of hypo- and hypersensitivity suggesting that these characteristics may be included in the BAP, potentially being beneficial as a behavioral phenotype in family genetics studies such as ours.