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Infants and the Emerging Autism Phenotype
While ASDs can reliably be diagnosed in children starting around 18-24 months of age, symptoms present much earlier. Converging evidence has pointed to a constellation of developmental differences in infants as young as 12 months, including limited eye contact, imitation, social smiling, receptive language, and affective sharing. This study enrolled infants and toddlers between the ages of 12 and 22 months who were exhibiting early behavioral features consistent with a diagnosis of ASD.
Objectives:
This study aimed to characterize symptoms of ASD emerging in infants evaluated as a part of a larger randomized control trial. Specifically, we aimed to understand whether chronological age and sibling status would predict differences in standardized measures of functioning and diagnosis.
Methods:
36 infants (M=17.81 months old, 83% male) were asked to participate in a series of assessments including the ADOS- Toddler Module, Mullen Scales of Early Learning and the clinician’s best estimate of diagnosis. Overall, infants demonstrated significant developmental delays with an average Mullen Early Learning Composite standard score of 67.58 (SD=13.36). Four scored “mild to moderate risk” classification on the ADOS- Toddler, with the remainder scoring with “moderate to severe risk”. The clinicians also rated their certainty that the infant met DSM criteria for ASD using the Diagnosis Data Form (Adapted from Cathy Lord, Personal Communication). A score of 15 reflects the highest score and the most diagnostic certainty. The scores of this sample ranged from 6-15 with an average score of 12.28 (SD=2.8).
Results:
Of the 36 infants who participated, 16 were first born and 20 had older siblings, 7 of whom had a diagnosis of ASD. Therefore, 19% of the total sample was infant siblings of children with ASD who were also showing early signs of the disorder. The child’s chronological age was not a significant predictor of overall developmental quotient score, ADOS total algorithm score or clinician’s diagnostic certainty. Infants with an older sibling with a diagnosis of ASD had significantly higher cognitive scores (M=77.86, SD=16.10) than children without a sibling (M=66.50, SD=11.63) with a diagnosis; t(33)=-2.33, p=.026). There were also trends toward infants with older siblings with confirmed diagnoses having lower ADOS total algorithm scores (M=15.57, SD=4.93) than those without (M=18.93, SD=4.29). Clinicians reported having more diagnostic certainty in those infants who did not have an affected older sibling (M=12.68, SD=2.28) compared to those who did (M=10.57, SD=4.28).
Conclusions:
This study examined the age related and sibling status differences in development amongst those children with the earliest signs of ASD. Although chronological age did not relate to the developmental or diagnostic outcomes, it may be that sibling status does play a role although larger samples are needed. Infants who belonged to the high risk group of infant siblings presented with less significant developmental delays, lower scores on the ADOS and clinicians rated less certainty in their overall diagnosis. These findings suggest that this subset of children may present with subtle delays early on but due to their sibling status parents may be more vigilant about monitoring these behaviors.