The Effects of Prospectively Following High-Risk Infant Siblings with ASD: Observation Positively Alters Outcome

Background: The past 10 years have seen a substantial increase in prospective studies of the infant siblings of children with autism spectrum disorder (ASD), whose risk of also having the condition is approximately 20%. Direct observation of this population from the first months and years of life provides a unique window into the early emergence of ASD. Despite the large number of infant siblings enrolled in prospective longitudinal research, few studies have examined how this early developmental surveillance may, in and of itself, influence development. Drawing on the concept of ‘the observer effect’ in physics—that the act of observing a phenomenon necessarily changes that phenomenon—this study investigates how prospective longitudinal surveillance may impact the course of a child’s development.

Objectives: Measure the effects of prospectively following infants later diagnosed with ASD on parent-reported first concerns, clinical presentation, and service utilization.

Methods: Children were selected to form two groups: 1) a prospectively-followed cohort (children who completed a prospective infant sibling study that included 10 visits from birth to 36 months); and 2) a community-referred cohort (children referred to the center for clinical assessment at a single time point). All children in each cohort: 1) received a clinical best-estimate diagnosis of ASD at 24-36 months; 2) had an older sibling already diagnosed with ASD; and 3) had completed measures of child demographics, development, and service use patterns. Cohorts were then matched on sex, race, cognitive ability, maternal age, maternal history of infertility, pregnancy complications, and gestational age (all factors known to impact parent-reported age of first concern), to yield final samples of n=18 prospectively-followed and n=18 community-referred.

Results: Parent-Reported First Concerns: Age of first concern was significantly earlier in the prospectively-followed cohort (11.7 months) than the community-referred cohort (15.5 months), p = .039. Furthermore, domains of first concern were more diverse in the prospectively-followed cohort (Figure 1). Clinical Presentation: The prospectively-followed cohort had lower ADOS severity scores (p = .027), and higher receptive (p = .013) and expressive (p = .011) language abilities relative to the community-referred cohort. Service Utilization: Although there were no differences in age at therapy onset, community-referred children were often enrolled in speech and occupational therapy, whereas prospectively-followed children were more often enrolled in comprehensive early intervention (p = .026). See Table 1b for all between-group comparisons.

Conclusions: Compared to a community-referred cohort, matched on age of diagnosis, sibling status, and other factors known to influence parent-reported first concerns (Table 1a), children enrolled in the longitudinal study had earlier and more diverse parent concerns, a higher enrollment rate into early intervention, and a less severe clinical presentation of autism symptom severity and language ability. These differences were observed despite similarities in nonverbal cognitive levels and parents’ experience with a child on the spectrum. These findings support early developmental surveillance as a framework in which to aid parents in early identification of a broad range of ASD symptoms, and to aid in accessing early intervention services for their children, likely to have profound positive cascading effects on future development.