Children with Autism Spectrum Disorders (ASDs) are impaired in visually disengaging attention in both social and non-social contexts, impairments that may, in subtler form, also affect the infant siblings of children with an ASD (ASD-sibs). We investigated patterns of visual attention (gazing) in six-month-old ASD-sibs (n = 17) and the siblings of typically developing children (COMP-sibs; n =17) during the Face-to-Face/Still-Face Protocol (FFSF), in which parents are sequentially responsive, nonresponsive, and responsive to their infants. Throughout the protocol, ASD-sibs shifted their gaze to and from their parents' faces less frequently than did COMP-sibs. The mean durations of ASD-sibs’ gazes away from their parents' faces were longer than those of COMP-sibs. ASD-sibs and COMP-sibs did not differ in the mean durations of gazes at their parents' faces. In sum, ASD-sibs showed no deficits in visual interest to their parents’ faces, but greater interest than COMP-sibs in non-face stimuli.
autism spectrum disorders; siblings; at-risk; disengagement; early deficits
Social referencing was investigated in 18-month-old siblings of children with autism spectrum disorders (ASD; “high-risk infants”). Infants were exposed to novel toys, which were emotionally tagged via adults’ facial and vocal signals. Infants’ information seeking (initiation of joint attention with an adult) and their approach/withdrawal behavior toward the toys before versus after the adults’ emotional signals was measured. Compared to both typically developing infants and high-risk infants without ASD, infants later diagnosed with ASD engaged in slower information seeking, suggesting that this aspect of referencing may be an early indicator of ASD. High-risk infants, both those who were and those who were not later diagnosed with ASD, exhibited impairments in regulating their behavior based on the adults’ emotional signals, suggesting that this aspect of social referencing may reflect an endophenotype for ASD.
Autism; Social referencing; Joint attention; Behavior regulation
To examine prospectively the emergence of behavioral signs of autism in the first years of life in infants at low and high risk for autism.
A prospective longitudinal design was used to compare 25 infants later diagnosed with an autism spectrum disorder (ASD) with 25 gender-matched low-risk children later determined to have typical development. Participants were evaluated at 6, 12, 18, 24, and 36 months of age. Frequencies of gaze to faces, social smiles, and directed vocalizations were coded from video and rated by examiners.
The frequency of gaze to faces, shared smiles, and vocalizations to others were highly comparable between groups at 6 months of age, but significantly declining trajectories over time were apparent in the group later diagnosed with ASD. Group differences were significant by 12 months of age on most variables. Although repeated evaluation documented loss of skills in most infants with ASD, most parents did not report a regression in their child’s development.
These results suggest that behavioral signs of autism are not present at birth, as once suggested by Kanner, but emerge over time through a process of diminishment of key social communication behaviors. More children may present with a regressive course than previously thought, but parent report methods do not capture this phenomenon well. Implications for onset classification systems and clinical screening are also discussed.
Autism; Onset; Infancy; Regression
We compared working memory (WM) for location of social vs. non-social targets in infant siblings of children with Autism Spectrum Disorders (sibs-ASD, n=25) and typically developing children (sibs-TD, n=30) at 6.5 and 9 months of age. There was a significant interaction of risk group and target-type on WM, in which the sibs-ASD had better WM for non-social targets as compared to controls. There was no group by stimulus interaction on two non-memory measures. The results suggest that the increased competency of sibs-ASD in WM (creating, updating, and using transient representations) for non-social stimuli distinguishes them from sibs-TD by 9 months of age. This early emerging strength is discussed as a developmental pathway that may have implications for social attention and learning in children at risk for ASD.
International research to understand infant patterns of development in autism spectrum disorders has recently focused on a research paradigm involving prospective longitudinal studies of infant siblings of children with autism. Such designs use a comparison group of infant siblings without any familial risks (the low- risk group) to gather longitudinal information about developmental skills across the first three years of life, followed by clinical diagnosis of ASD at 36 months. This review focuses on five topics: presence of ASD in the infant sibling groups, patterns and characteristics of motor development, patterns and characteristics of social and emotional development, patterns and characteristics of intentional communication, both verbal and nonverbal, and patterns that mark the onset of behaviors pathognomonic for ASD. Symptoms in all these areas typically begin to be detected during the age period of 12 –24 months in infants who will develop autism. Onset of the symptoms occurs at varying ages and in varying patterns, but the pattern of frank loss of skills and marked regression reported from previous retrospective studies in 20–30% of children is seldom reported in these infant sibling prospective studies. Two surprises involve the very early onset of repetitive and unusual sensory behaviors, and the lack of predictive symptoms at age 6 months. Contrary to current views that autism is a disorder that profoundly affects social development from the earliest months of life, the data from these studies presents a picture of autism as a disorder involving symptoms across multiple domains with a gradual onset that changes both ongoing developmental rate and established behavioral patterns across the first two to three years of life.
This study examined the communicative profiles of children with autism spectrum disorders (ASD) in the second year of life.
Communicative acts were examined in 125 children 18 to 24 months of age: 50 later diagnosed with ASD; 25 with developmental delays (DD); and 50 with typical development (TD). Precise measures of rate, functions, and means of communication were obtained through systematic observation of videotaped Behavior Samples from the Communication and Symbolic Behavior Scales Developmental Profile (Wetherby & Prizant, 2002).
Children with ASD communicated at a significantly lower rate than children with DD and TD. The ASD group used a significantly lower proportion of acts for joint attention and a significantly lower proportion of deictic gestures with a reliance on more primitive gestures compared to DD and TD. Children with ASD who did communicate for joint attention were as likely as other children to coordinate vocalizations, eye gaze, and gestures. Rate of communicative acts and joint attention were the strongest predictors of verbal outcome at age 3.
By 18 to 24 months of age, children later diagnosed with ASD showed a unique profile of communication, with core deficits in communication rate, joint attention, and communicative gestures.
•Prospective studies of infants at familial risk are characterizing developmental pathways to ASD.•Children with ASD show social and communication difficulties in the second year of life.•Early neurocognitive markers include atypical neural response to gaze and slowed disengagement.•Mapping how ASD unfolds from birth is central to early identification and intervention.
Autism Spectrum Disorders (ASDs) are neurodevelopmental disorders characterized by impairments in social interaction and communication, and the presence of restrictive and repetitive behaviors. Symptoms of ASD likely emerge from a complex interaction between pre-existing neurodevelopmental vulnerabilities and the child's environment, modified by compensatory skills and protective factors. Prospective studies of infants at high familial risk for ASD (who have an older sibling with a diagnosis) are beginning to characterize these developmental pathways to the emergence of clinical symptoms. Here, we review the range of behavioral and neurocognitive markers for later ASD that have been identified in high-risk infants in the first years of life. We discuss theoretical implications of emerging patterns, and identify key directions for future work, including potential resolutions to several methodological challenges for the field. Mapping how ASD unfolds from birth is critical to our understanding of the developmental mechanisms underlying this disorder. A more nuanced understanding of developmental pathways to ASD will help us not only to identify children who need early intervention, but also to improve the range of interventions available to them.
ASD; Autism; Infant sibling; High-risk; Causal path; Developmental mechanisms
Infants and preschoolers with ASD show impairment in their responses to other people's distress relative to children with other developmental delays and typically developing children. This deficit is expected to disrupt social interactions, social learning, and the formation of close relationships. Response to distress has not been evaluated previously in infants with ASD earlier than 18 months of age.
Participants were 103 infant siblings of children with autism and 55 low-risk controls. All children were screened for ASD at 36 months and 14 were diagnosed with ASD. Infants' responsiveness to distress was evaluated at 12, 18, 24, and 36 months. An examiner pretended to hit her finger with a toy mallet and infants' responses were video-recorded. Attention to the examiner and congruent changes in affect were coded on four-point Likert scales.
Cross-sectional and longitudinal analyses confirm that the ASD group paid less attention and demonstrated less change in affect in response to the examiner's distress relative to the high-risk and low-risk participants who were not subsequently diagnosed with ASD. Group differences remained when verbal skills and general social responsiveness were included in the analytic models.
Diagnostic groups differ on distress response from 12 to 36 months of age. Distress-response measures are predictive of later ASD diagnosis above and beyond verbal impairments. Distress response is a worthwhile target for early intervention programs.
autism; early identification; siblings; empathy; infancy
We observed infant siblings of children with autism later diagnosed with ASD (ASD siblings; n = 17), infant siblings of children with autism with and without other delays (Other Delays and No Delays siblings; n = 12 and n = 19, respectively) and typically developing controls (TD controls; n = 19) during a free-play task at 18 months of age. Functional, symbolic, and repeated play actions were coded. ASD siblings showed fewer functional and more non-functional repeated play behaviors than TD controls. Other Delays and No Delays siblings showed more non-functional repeated play than TD controls. Group differences disappeared with the inclusion of verbal mental age. Play as an early indicator of autism and its relationship to the broader autism phenotype is discussed.
Autism spectrum disorders; Functional play; Symbolic play; Repetitive behaviors; Play; Infant siblings of children with autism
We examined social attention and attention shifting during (a) a play interaction between 12-month olds and an examiner and (b) after the examiner pretended to hurt herself. We coded the target and duration of infants’ visual fixations and frequency of attention shifts. Siblings of children with autism and controls with no family history of autism were tested at 12 months and screened for ASD at 36 months. Groups did not differ on proportion of attention to social stimuli or attention shifting during the play condition. All groups demonstrated more social attention and attention shifting during the distress condition. Infants later diagnosed with ASD tended to continue looking at a toy during the distress condition despite the salience of social information.
Autism; Broader autism phenotype; Visual attention; Attention shifting; Early identification
Motor delays have been reported in retrospective studies of young infants who later develop Autism Spectrum Disorders (ASDs).
In this study, we prospectively compared the gross motor development of a cohort at risk for ASDs; infant siblings of children with ASDs (AU sibs) to low risk typically developing (LR) infants.
24 AU sibs and 24 LR infants were observed at 3 and 6 months using a standardized motor measure, the Alberta Infant Motor Scale (AIMS). In addition, as part of a larger study, the AU sibs also received a follow-up assessment to determine motor and communication performance at 18 months using the Mullen Scales of Early Learning.
Significantly more AU sibs showed motor delays at 3 and 6 months than LR infants. The majority of the AU sibs showed both early motor delays and later communication delays.
Small sample size and limited follow-up.
Early motor delays are more common in infant AU sibs than LR infants. Communication delays later emerged in 67–73% of the AU sibs who had presented with early motor delays. Overall, early motor delays may be predictive of future communication delays in children at risk for autism.
Motor; Communication; Language; Autism; Infants; Early identification
Core impairments in social and communicative behaviors are among the defining characteristics of autism spectrum disorder (ASD), making this a model syndrome for investigating the mechanisms that underlie social cognition and behavior. Current research is exploring the origins of social impairments in prospective longitudinal studies of infants who are at high risk for ASD, defined as having an older sibling with the disorder. Behavioral studies that have followed these infants through to outcomes have found that during the early months of life they are no different from typically developing infants; they are socially interested, engaged and enjoy interactions with people. By the end of the first year risk signs for later ASD can be identified though no single marker has been identified. It seems that an aggregate of risk markers together may be need to predict ASD. Other studies have compared infants at risk for ASD to low risk controls to identify neurocognitive endophenotypes. Several differences in subtle aspects of behavior and in brain organization have been found in infants younger than 12 months, though it is not known whether these differences are also risk markers for a later ASD diagnosis. The findings from these line of research are used to provide a new view of ASD, as a disorder defined on the basis of alterations in the developmental trajectories across multiple domains. ASD is an emergent disorder that is characterized by the loss of social communication skills in the period between 9 and 24 months. Across children the rate, timing and severity of this loss is highly variable. Future research will lead to a greater understanding of the genetic and neurocognitive mechanisms that underlie these fundamental changes in the developmental patterns of individuals with ASD.
Social inattention is common in children with autism whereas associative learning capabilities are considered a relative strength. Identifying early precursors of impairment associated with autism could lead to earlier identification of this disorder. The present study compared social and nonsocial visual attention patterns as well as associative learning in infant siblings of children with autism (AU sibs) and low risk (LR) infants at six months of age.
25 AU sibs and 25 LR infants were observed in a novel social-object learning task, within which attention to social and non-social cues was contrasted. Video recorded data were coded for percent duration of gaze to objects or caregiver. Movement rates to activate the toy within the associative learning task were also quantified.
Both groups learned the association between moving a switch and activating a cause-effect toy. AU sibs spent less time looking at caregivers and more time looking at the toy or joystick when their caregivers made no attempts to engage their attention. However, response to caregiver-initiated social bids was comparable for both groups.
Infrequent self-initiated socially directed gaze may be an early marker of later social and communication delays.
Attention; Autism; Infants; Social; Learning
Objective. The purpose of the study was to compare the cognitive skills of young children diagnosed with autism spectrum disorder (ASD) to same-aged peers referred for possible developmental delays or behavioral concerns using the Bayley Scales of Infant Development-Third Edition. Method. A retrospective chart review was conducted of 147 children ages 16 to 38 months who were referred to a diagnostic clinic for developmental evaluation. Children with ASD were compared to those without ASD with respect to cognition and language outcomes, both overall and by age.
Results. While language skills in children with ASD were more significantly delayed than language skills in children without ASD, there was less discrepancy in the cognitive skills of children with and without ASD.
Conclusion. Formal cognitive assessment of children with ASD can provide guidance for developmental expectations and educational programming. Cognitive skills of children with ASD may be underappreciated.
Evidence from prospective high-risk infant studies suggests that early symptoms of autism usually emerge late in the first- or early in the second-year of life after a period of relatively typical development. This is the first neuroimaging study to prospectively examine white matter fiber tract organization during this interval in infants who develop autism spectrum disorder (ASD) by 24 months.
Participants included 92 infant siblings from an ongoing imaging study of autism. All participants had diffusion tensor imaging at 6 months and behavioral assessments at 24 months, with a majority contributing additional imaging data at either or both 12 and 24 months. At 24 months, 28 infants met criteria for ASD; 64 infants did not. Microstructural properties of white-matter fiber tracts reported to be associated with ASD or related behaviors were characterized by fractional anisotropy (FA) and radial and axial diffusivity.
FA trajectories differed significantly between infants who did versus did not develop ASD for 12 of 15 fiber tracts. Development for most fiber tracts in infants with ASD was characterized by elevated FA at 6 months followed by slower developmental change overtime relative to infants without ASD. Thus, by 24 months of age, lower FA values were evident for those with ASD.
These results suggest that the aberrant development of white matter pathways precede the manifestation of autistic symptoms in the first year of life. Longitudinal data are critical to characterizing the dynamic age-related brain and behavior changes underlying this neurodevelopmental disorder.
Extremely preterm (EP) infants screen positive for Autism Spectrum Disorders (ASD) at high rates. However it is not clear whether this is due to high rates of ASD in EPs or to high rates of false positive screens for ASD in children with a high rate of underlying neurodevelopmental impairments. Combining a parent questionnaire designed to distinguish developmental delay from ASD with direct observation of infant behavior may more accurately screen for ASD in EPs.
To determine rates of positive screen for ASD at 18–22months(m) in EPs using three screens; to determine factors associated with a positive screen.
554 infants born <27 weeks were screened at 18–22m using the Pervasive Developmental Disorders Screening Test, 2nd edition, Stage 2 (PDDST-II) and the response to name and response to joint attention items from the Autism Diagnostic Observation Schedule. Infants with severe cerebral palsy, deafness and blindness were excluded. Associations between positive screen and neonatal/infant characteristics were determined.
113/554 (20 %) had ≥1 positive screen. 10% had a positive PDDST-II, 6% response to name, 9% response to joint attention; in only 1% were all 3 screens positive. Positive screen was associated with male gender, more hospital days, white race, lower maternal education, abnormal behavioral scores, and cognitive/language delay.
The use of three screens for ASD in EPs results in higher screen positive rates than use of one screen alone. Diagnostic confirmation is needed before true rates of ASD in EPs are known.
Autism; Prematurity; Screening
We explored social information processing and its relation to social and communicative symptoms in toddlers with Autism Spectrum Disorder (ASD) and their siblings. Toddlers with more severe symptoms of autism showed slower habituation to faces than comparison groups; slower face learning correlated with poorer social skills and lower verbal ability. Unaffected toddlers who were siblings of children with ASD also showed slower habituation to faces compared with toddlers without siblings with ASD. We conclude that slower rates of face learning may be an endophenotype of ASD and is associated with more severe symptoms among affected individuals.
Habituation; Autism/ASD; Face processing; Toddlers; Broader phenotype
A rise in the prevalence of diagnosed cases of autism spectrum disorder (ASD) has been reported in several studies in recent years. While this rise in ASD prevalence is at least partially related to increased awareness and broadened diagnostic criteria, the role of environmental factors cannot be ruled out, especially considering that the cause of most cases of ASD remains unknown. The study of families with multiple affected children can provide clues about ASD etiology. While the majority of research on ASD multiplex families has focused on identifying genetic anomalies that may underlie the disorder, the study of symptom severity across ASD birth order may provide evidence for environmental factors in ASD. We compared social and cognitive measures of behavior between over 300 first and second affected siblings within multiplex autism families obtained from the Autism Genetic Resource Exchange dataset. Measures included nonverbal IQ assessed with the Ravens Colored Progressive Matrices, verbal IQ assessed with the Peabody Picture Vocabulary Test, and autism severity assessed with the Social Responsiveness Scale (SRS), an instrument established as a quantitative measure of autism. The results indicated that females were more severely impacted by ASD than males, especially first affected siblings. When first and second affected siblings were compared, significant declines in nonverbal and verbal IQ scores were observed. In addition, SRS results demonstrated a significant increase in autism severity between first and second affected siblings consistent with an overall decline in function as indicated by the IQ data. These results remained significant after controlling for the age and sex of the siblings. Surprisingly, the SRS scores were found to only be significant when the age difference between siblings was less than 2 years. These results suggest that some cases of ASD are influenced by a dosage effect involving unknown epigenetic, environmental, and/or immunological factors.
When do infants begin to communicate positive affect about physical objects to their social partners? We examined developmental changes in the timing of smiles during episodes of initiating joint attention that involved an infant gazing between an object and a social partner. Twenty-six typically developing infants were observed at 8, 10, and 12 months during the Early Social-Communication Scales, a semistructured assessment for eliciting initiating joint attention and related behaviors. The proportion of infant smiling during initiating joint attention episodes did not change with age, but there was a change in the timing of the smiles. The likelihood of infants smiling at an object and then gazing at the experimenter while smiling (anticipatory smiling) increased between 8 and 10 months and remained stable between 10 and 12 months. The increase in the number of infants who smiled at an object and then made eye contact suggests a developing ability to communicate positive affect about an object.
The recurrence risk of autism spectrum disorders (ASD) is estimated to be between 3% and 10%, but previous research was limited by small sample sizes and biases related to ascertainment, reporting, and stoppage factors. This study used prospective methods to obtain an updated estimate of sibling recurrence risk for ASD.
A prospective longitudinal study of infants at risk for ASD was conducted by a multisite international network, the Baby Siblings Research Consortium. Infants (n = 664) with an older biological sibling with ASD were followed from early in life to 36 months, when they were classified as having or not having ASD. An ASD classification required surpassing the cutoff of the Autism Diagnostic Observation Schedule and receiving a clinical diagnosis from an expert clinician.
A total of 18.7% of the infants developed ASD. Infant gender and the presence of >1 older affected sibling were significant predictors of ASD outcome, and there was an almost threefold increase in risk for male subjects and an additional twofold increase in risk if there was >1 older affected sibling. The age of the infant at study enrollment, the gender and functioning level of the infant's older sibling, and other demographic factors did not predict ASD outcome.
The sibling recurrence rate of ASD is higher than suggested by previous estimates. The size of the current sample and prospective nature of data collection minimized many limitations of previous studies of sibling recurrence. Clinical implications, including genetic counseling, are discussed.
autism; recurrence; sibling risk
While it is well-known that individuals with autism spectrum disorder (ASD) have difficulties processing faces, very little is known about the origins of these deficits. The current study focused on 6- and 11-month-old infants who were at either high-risk (n = 43) or low-risk (n = 31) for developing ASD based on having a sibling already diagnosed with the disorder. Eye-tracking data were collected while the infants viewed color photographs of faces. Similar to previous studies with both typically developing adults and infants, low-risk infants demonstrated a preference for looking at the left side of the face (known as a left visual field bias) that emerged by 11 months of age. In contrast, high-risk infants did not demonstrate a left visual field bias at either age. Comparisons of the amount of attention given to the eye versus mouth regions indicated no differences between the two risk groups.
infants; autism; face perception; cognition
Siblings of children with autism (sibs-A) are at increased genetic risk for autism spectrum disorders (ASD) and milder impairments. To elucidate diversity and contour of early developmental trajectories exhibited by sibs-A, regardless of diagnostic classification, latent class modeling was used.
Sibs-A (n=204) were assessed with the Mullen Scales of Early Learning from age 6–36 months. Mullen T scores served as dependent variables. Outcome classifications at age 36 months included: ASD (n=52); non-ASD social/communication delay (broader autism phenotype; BAP) (n=31); and unaffected (n=121). Child-specific patterns of performance were studied using latent class growth analysis. Latent class membership was then related to diagnostic outcome through estimation of within-class proportions of children assigned to each diagnostic classification.
A 4-class model was favored. Class 1 represented accelerated development and consisted of 25.7% of the sample, primarily unaffected children. Class 2 (40.0% of the sample), was characterized by normative development with above-average nonverbal cognitive outcome. Class 3 (22.3% of the sample) was characterized by receptive language, and gross and fine motor delay. Class 4 (12.0% of the sample), was characterized by widespread delayed skill acquisition, reflected by declining trajectories. Children with an outcome diagnosis of ASD were spread across Classes 2, 3, and 4.
Results support a category of ASD that involves slowing in early non-social development. Receptive language and motor development is vulnerable to early delay in sibs-A with and without ASD outcomes. Non-ASD sibs-A are largely distributed across classes depicting average or accelerated development. Developmental trajectories of motor, language, and cognition appear independent of communication and social delays in non-ASD sibs-A.
autism; trajectories; broader autism phenotype
Previous research has indicated that children with autism exhibit accelerated head growth (HG) in infancy, although the timing of acceleration varies between studies. We examined infant HG trajectory as a candidate autism endophenotype by studying sibling pairs.
We retrospectively obtained serial head orbitofrontal circumference measurements of: a) 48 sibling pairs in which one (n=28) or both (n=20) sibs were affected by an autism spectrum disorder (ASD); and b) 85 control male sibling pairs.
Rate of HG of ASD subjects was slightly accelerated compared to controls, but the magnitude of difference was below the limit of reliability of standard measurement methods. Sibling intra class correlation for rate of HG was highly statistically significant; the magnitude was significantly stronger among autism-affected families (ICC=.63) than among controls (ICC=.26), p<.01.
Infant HG trajectory appears familial—possibly endophenotypic—but was not a reliable marker of autism risk among siblings of ASD probands in this sample.
infancy; head circumference; brain growth; autism; endophenotype; pervasive developmental disorder
From early infancy onwards, young children appear motivated to engage reciprocally with others and share psychological states during dyadic interactions. Although poor reciprocity is one of the defining features of autism spectrum disorders (ASDs), few studies have focused on the direct assessment of real-life reciprocal behavior; consequently, our knowledge of the nature and the development of this core feature of autism is still limited. In this study, we describe the phenomenon of reciprocity in infant-caregiver interaction by analyzing family movies taken during the first year of life of 10 infants with ASD and 9 infants with typical development (TD). We analyzed reciprocal behaviors by means of a coding scheme developed for this purpose (caregiver-infant reciprocity scale (CIRS)). Infants with ASD displayed less motor activity during the first semester and subsequently fewer vocalizations, compared to TD infants. Caregivers of ASD infants showed in the second semester shorter periods of involvement and a reduction of affectionate touch. These results suggest that from the first months of life a nonsynchronic motor-vocal pattern may interfere in different ways with the development of reciprocity in the primary relationship between infants later diagnosed with ASD and their caregivers.
Siblings of children with autism have an increased risk for autism spectrum disorders (ASD). As children with autism often exhibit an atypical trajectory of head circumference (HC) growth, HC may be an indicator of vulnerability to autism. This study investigated whether infant siblings of children with ASD (n = 77) with an atypical trajectory of HC growth were more likely than those without an atypical HC trajectory to develop autism symptoms. Results showed that infants who had larger HC at 12 months, and whose HC growth rate decelerated more rapidly between 12 and 24 months were more likely to exhibit autism symptoms than infants with more typical HC trajectories. Among infant siblings of children with autism, atypical HC growth might alert pediatricians to provide screening and/or referral for further evaluation.
Autism; Head circumference; Infant siblings