Despite limitations of a single site study, modest sample size and limits to generalisability, autism sibling recurrence in family history infants may be higher in midâchildhood than in studies reporting diagnostic outcome at 3âyears.
Abstract Autism sibling recurrence in prospective infant family history studies is ~20% at 3âyears but systematic followâup to midâchildhood is rare. In population and clinical cohorts autism is not recognized in some children until schoolâage or later. One hundred and fiftyânine infants with an older sibling with autism underwent research diagnostic assessments at 3âyears and midâchildhood (6 to 12âyears (mean 9)). We report the autism sibling recurrence rate in midâchildhood and compare developmental and behavioral profiles at midâchildhood and 3âyears 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 midâchildhood was 37.1%, 95% CI [29.9%, 44.9%] and higher in boys than girls. Around half of those diagnosed with autism in midâchildhood had not received a diagnosis at 3âyears. Later, diagnosis was more common in girls than boys. While some had subâthreshold 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 midâchildhood than in studies reporting diagnostic outcome at 3âyears. Findings have implications for families and clinical services, and for prospective family history studies.