Autism: Social and Communication Predictors in Siblings

Principal Investigator: Rebecca Landa

This is a longitudinal study of Autism Spectrum Disorders (ASD). Six groups will be assessed longitudinally. Group 1: siblings of probands with autism; (Group 2) late talkers having no family history of autism; (Group 3) typically-developing controls; (Group 4) premature controls (for the motor learning paradigms, only); (Group 5) children with autism who did not participate in the 0-36 month assessments (may be probands/siblings of children in Group 1); (Group 6) children with developmental delays (such as Down Syndrome). Groups will be matched for gender, SES, race, and birth order. These six groups of infants and toddlers will receive assessments designed to provide a general index of their development as well as extensive measurement of JA, shared positive affect, imitation, and communication. 500 infant siblings (rather than the originally requested 100) of children with autism, 100 (rather than the originally requested 25) controls, 60 late-talkers, and 40 (rather than the originally requested 15) premature controls will be ascertained. 50 children with developmental delays will be ascertained; these children may enter at any age between 0-36 months old. Testing will be conducted from birth through 36 months of age, and annually at ages 4 through 12 years. Participants enter the study between birth and 18-months of age. Participants who return annually for testing at ages 9, 10, 11, and 12 years will have already participated in the study before the age of 8 years old. Additionally, 50 participants at each data point (6, 10, 14, 18, 24, 30, and 36 months) will be recruited to be examined cross-sectionally instead of longitudinally. The late-talkers (Group 2) will have their first assessment at 18-months of age and will follow the testing schedule of the other groups. The premature controls (Group 4) will enter for age-adjusted 3-month and 6-month visits, plus the 18-month visit. The children with autism who did not participate in the 0-36 month assessments (Group 5) will enter between ages 4-8 years. The visit at 36 months of age is when we determine preliminary “outcome” of participants, and there is additional testing at this visit for communication and ASD. If parents or staff have any concern about a child's development between scheduled visits, the child may visit the lab for additional assessment, using the measures described below. Of the children who will be participating in the study, 100 will be tested in Boston at Spaulding Hospital under the direction of Dr. Margaret Bauman. Spaulding Hospital has a separate IRB and all changes approved by the Johns Hopkins Medicine IRB will be approved there.

In addition, we are including up to 50 “children of interest” [added in the 2006 renewal] who do not meet standard eligibility criteria. There are two categories of such children: children who are already participating in the study but whom we later determine were not eligible (e.g., discovery of distant relative with ASD; “late-talker” whom we determine has autism) and children whom we would like to bring into the study that would be of extreme interest to the scientific and medical communities (e.g., 6-month old with clear signs of autism, but without an older affected sibling).

There will also be a small number of children aged 0-8 years who may come in for practice testing; these children will be given some or all of the assessments for their age range, but their data will not be used for analyses or publication. The time commitment involved will be at the family’s discretion.

Specific Aim #1: To identify behavioral profiles that enhance diagnosis of ASD in the first two years of life.

Specific Aim #2: To test hypotheses about the relationship between joint attention (JA), shared positive affect, and communication in three groups of infants: those later diagnosed with ASD, those later diagnosed with non-autism language impairment, and in typically developing children ('diagnosis' made at 3 years of age).

Specific Aim #3: To develop diagnostic criteria for autism by 18 months of age through the study of late talkers, some of whom are at high risk for autism (i.e., siblings of children with autism).

Hypothesis 1: Early impairment in social engagement (joint attention, shared positive affect) and social communication is predictive of ASD characteristics at three years of age in siblings of children with autism. Specifically, based on inferences from the literature and our pilot data, we predict that, in infant siblings of children with autism who are themselves later diagnosed with ASD:
A. Joint attention processes (joint engagement, comprehension of joint attention signals, and initiation of communication for establishing joint attention) will be impaired at 14 and 24 months;
B. Shared positive affect during social communicative events will be impaired;
C. Infant siblings of children with autism who are not subsequently diagnosed with ASD will not show impairment of joint attention or shared positive affect during social communicative events. Neither the children with ASD nor those who are unimpaired will exhibit deficits in non-social, instrumental, object-based initiations (referred to here as ‘behavior regulation of adults’).

Hypothesis 2a: An impairment in shared positive affect is linked to the development of joint attention skills in children with ASD. Affect is the first channel of reciprocal communication for an infant. During the second year of life, typically developing children display shared positive affect within object-based joint attention interactions with their caregiver, rather than during solitary interaction with objects (Adamson & Bakeman, 1985). Yet there is evidence that this will not be the case for children with ASD, who appear to prefer solitary activity with objects that provide salient perceptual experiences to interactions with others. We will compare the display of positive affect across interactive versus non-interactive contexts and during social versus non-social communicative exchanges in autism sibs.

Hypothesis 2b: A limited repertoire of communicative forms (including gestures, speech sounds in prelinguistic vocalizations, words and word combinations) used for communicative purposes will be observed in children with impaired joint attention and shared positive affect. This is based on literature indicating the essential role that comprehension of joint attention signals plays in language acquisition.

Hypothesis 3: A constellation of nonlinguistic behaviors important for preverbal and verbal communication will differentiate autism from language delayed toddlers without autism at 18 months of age. These behaviors share the concept of interpersonal synchrony and specifically involve measures of joint attention, shared positive affect, and imitation, which have known developmental trajectories in typical development.

Early diagnosis and intervention are critical for ASD in order to take advance of neuroplasticity in the developing brain; however, ASD is rarely diagnosed before three years of age. The infant siblings of children with autism are at high-risk for developing autism themselves, and thus provide a population that will allow us to track the development of autism. This is the first large-scale, prospective, longitudinal study of the development of autism.