Temperament Differences Across the First Three Years in High-Risk Younger Siblings of Children with ASD Compared to Low-Risk Controls
Temperament differences between high-risk children who do and do not develop ASD have been noted during the first few years of life (Clifford et al., 2013; del Rosario et al., 2014).
To examine differences in child temperament characteristics in the first three years in a high-risk group of children who have an older sibling with ASD compared to a low-risk control group using a prospective, longitudinal design.
Parents rated child temperament characteristics on the Carey Temperament Scales (Carey & McDevitt, 1995) for younger siblings of a child with ASD (N=157, 90 males) and low risk control children (N=23, 12 males) with no family history of ASD at 6-, 14-, 24-, and 36-months. The Autism Diagnostic Observation Schedule (ADOS; Lord et al., 2002; 2012) and Mullen Scales of Early Learning (MSEL; Mullen, 1995) were administered at each visit. At 36-months, children were categorized as high risk ASD (HR-ASD, n=32), high risk non-ASD (HR non-ASD, n=125) or low risk typically developing (LR, n=23) based on results of the ADOS and clinical best estimate.
Nonparametric Kruskal-Wallis tests, followed by Mann-Whitney U tests for comparisons, were used to analyze temperament differences between the three diagnostic groups from 6-36 months. Results were considered significant with p-values<.01 or lower. At 6 months, there was a trend for group differences for Intensity (p=.037). After removing an outlier, group differences were significant (p=.01). HR-ASD group was rated as lower in Intensity (i.e., more passive) than the HR non-ASD and LR groups (ps<.01), but the latter two groups did not differ. At 14 months, there were differences between groups for Distractability, Rhythmicity, and Threshold for Noticing New Stimuli (ps<.01). HR-ASD group was harder to distract from what they were interested in compared to the HR non-ASD and LR groups, and more arrhythmic than the LR group (ps<.01). The HR non-ASD group needed a higher threshold before noticing new stimuli compared to the LR group but not the HR-ASD group; the latter two groups did not differ. At 24 months, there were group differences for Adaptability, Rhythmicity, and Distractability (ps<.01). The HR-ASD group had greater difficulties with Adaptability and Rhythmicity than LR group, and were harder to distract from what they were interested in and more arrhythmic compared to the HR non-ASD group (ps<.01). At 36 months, there were group differences for Adaptability, Distractability, Mood, Persistence, and Threshold for Noticing New Stimuli. HR-ASD group had greater difficulties with Adaptability and more Negative Mood compared to LR group, and had greater difficulty with Adaptability, Distractability, Persistence, and Threshold for Noticing New Stimuli compared to HR non-ASD group (ps<.01).
Conclusions: In this prospective, longitudinal study, temperament differences between high-risk children who developed ASD and typically developing controls were noted as early as 6 months of age and continued through 36 months. This is consistent with findings that children with ASD tend to be more passive in infancy compared to infants without ASD, with notable difficulties in self-regulation of temperament in the second and third years.