Reliable methods for the detection of autism prior to age 2 are lacking, preventing access for at-risk infants to efficacious early intervention. Analysis of differences in responses to sensation between typically developing infants and infants who later develop or are at-risk for autism has been proposed as one way of identifying risk for autism at earlier ages. Previous studies examining sensory differences between young children who are later diagnosed with autism and those who are not have been mixed in the literature. The variability of results in the literature regarding sensory behaviors as an early sign of autism makes it an area of interest for further research and exploration.
Objectives: The objective of this study was to evaluate whether infants aged 2, 4 and 6 months at high risk for autism differed in responses to touch and sound stimulation and mouthing behavior from infants not at risk for autism.
Methods:
A high-risk group (HR, n=24) contained participants with an older sibling or first cousin with autism and a second group included participants with no known family history of autism (LR, n=15). Participants were involved in a larger longitudinal study examining early signs of autism. Infants were assessed at regular time intervals from 2-18 months of age. For the purposes of this study, we evaluated sensory behavior in the first 6 months of life only. Videos of infants at ages 2, 4 and 6 months performing developmental assessments were coded for mouthing and responses to touch and sound stimuli. Video footage was standardized and only time that the infant spent in supine was evaluated for mouthing and touch. Time spent in supine and seated positions was evaluated for sound stimuli. Mouthing duration and frequency was recorded with minimum threshold duration of two seconds. Responses to touch and sound stimuli were evaluated utilizing a standardized coding protocol that captured orientation, startle, aversive, seeking, or appropriate responses. Videos were coded by two independent raters and inter-rater reliability of at least 90% was achieved at each time point. Data was analyzed visually using frequency plots comparing HR and LR on each variable and each time point. Variables of interest were further explored using chi-square analysis.
Results: Preliminary results reveal significant differences between groups at 2 months of age on the likelihood of responding typically to unexpected sound in supine (χ2= 4.95, p<.05, df=1) and atypically to unexpected sound in supine (χ2= 4.29, p<.05, df=1), with HR subjects more likely to respond atypically. A non-significant trend indicated that the HR group was more likely not to mouth than the LR group at 4 months (χ2 = 3.07, p>.05, df=1) and indicated a delayed trajectory of mouthing development between 2-6 months on visual inspection. No differences in response to touch were noted between HR and LR groups at any time point.
Conclusions: These results indicate that further investigation of early mouthing behavior and response to unexpected sound may reveal new early markers of autism that would improve efforts towards earlier identification.
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See more of: Symptoms, Diagnosis & Phenotype