Mid-childhood autism sibling recurrence in infants with a family history of autism

Abstract

Autism sibling recurrence in prospective infant family history studies is ~20% at 3 years but systematic follow-up to mid-childhood is rare. In population and clinical cohorts autism is not recognized in some children until school-age or later. One hundred and fifty-nine infants with an older sibling with autism underwent research diagnostic assessments at 3 years and mid-childhood (6 to 12 years (mean 9)). We report the autism sibling recurrence rate in mid-childhood and compare developmental and behavioral profiles at mid-childhood and 3 years in those with earlier versus later recognized autism, and those who had, or had not, received a community autism diagnosis. The autism recurrence rate in this sample in mid-childhood was 37.1%, 95% CI [29.9%, 44.9%] and higher in boys than girls. Around half of those diagnosed with autism in mid-childhood had not received a diagnosis at 3 years. Later, diagnosis was more common in girls than boys. While some had sub-threshold symptoms at 3, in others late diagnosis followed a largely typical early presentation. Sibling recurrence based on community clinical diagnosis was 24.5%, 95% CI [18.4%, 31.9%]. Those who also had a community diagnosis tended to be older, have lower adaptive function and higher autism and inattention symptoms. Notwithstanding limitations of a single site study, modest sample size and limits to generalisability, autism sibling recurrence in family history infants may be higher in mid-childhood than in studies reporting diagnostic outcome at 3 years. Findings have implications for families and clinical services, and for prospective family history studies.

Keywords: autism; diagnosis; family history; infants; recurrence likelihood; siblings.

FIGURE 1

3‐year and mid‐childhood scores by earlier versus later diagnosed. To contrast scores of the Early versus Later diagnosed groups on the developmental and autism measures used at 3‐years and mid‐childhood z‐scores derived separately for each measure from the current sample at each timepoint are shown. IQ, Mullen ELC (3‐Year)/WASI FSIQ (Mid‐Childhood); ABC, Vineland Adaptive Behavior Composite; ADOS‐2 CSS, Autism Diagnostic Observation Schedule‐2 total Calibrated Severity Score, ADI‐R, Autism Diagnostic Interview‐Revised; Social, Social domain; Comm, Communication domain; RRB, Restricted and repetitive behaviors domain; SCQ, Social Communication Questionnaire, SRS, Social Responsiveness Scale T‐score.