Cognitive and behavioral differences in toddlers with autism spectrum disorder from multiplex and simplex families

Abstract

Prospective, longitudinal designs utilizing “high‐risk” infant siblings of children diagnosed with Autism Spectrum Disorder (ASD‐sibs) have provided unique and valuable insights regarding the early ASD phenotype. However, it remains unclear whether these cases are representative of all children with ASD. The objective in the present study was to investigate whether the early development of toddlers with ASD from multiplex (MPX) families, who have an affected older sibling, is similar or different to toddlers with ASD from simplex (SPX) families, where there is no affected sibling. A further aim was to examine patterns of association between autism symptom severity and cognitive functioning within each group to inform possible mechanisms for group similarities/differences. Behavioral and cognitive assessment data from a sample of toddlers with ASD was utilized, comprising 45 MPX, 127 first‐born SPX, and 72 later‐born SPX toddlers. Participants in the MPX group had significantly higher developmental quotients on the Mullen Scales of Early Learning compared to those in the SPX groups, who did not differ from each other. However, all three groups were similar on their autism severity scores (measured using the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview), and the pattern of relationships between cognitive ability and autism symptom severity. The results suggest that caution be exercised in generalizing findings from ASD‐sib samples to other samples of children with ASD. The higher cognitive abilities in the MPX group, in addition to biological differences, may also be an outcome of family environmental factors, which deserves further investigation. Autism Research 2019, 12: 682–693. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. Lay Summary We sought to establish whether toddlers with autism from families where there is more than one affected child, called multiplex families, are different to children from simplex families, where there is only one affected child, and no other members within the immediate family with an autism diagnosis. We found that while toddlers from multiplex families were similar to those from simplex families in their autism symptoms, they were more developmentally advanced than children in the latter group.

The course and prognostic capability of motor difficulties in infants showing early signs of autism

“…Infant siblings who do go on to receive a diagnosis of ASD may have different genetic and environmental developmental influences than the broader ASD population. For example, there is evidence for different phenotypes among children with ASD from simplex (only child in family with an ASD diagnosis) and multiplex (multiple children with a diagnosis of ASD) families (Dissanayake et al, 2019). An alternate method of studying infants at increased likelihood of ASD is through the recruitment of infants confirmed with early behavioral characteristics closely aligned to the ASD phenotype, such as infants with very early social and/or communication difficulties.…”

DAS‐IICognitive Profiles Are Not Diagnostically Meaningful For Autism: AROCAnalysis

“…The SSC sample included only simplex ASD individuals, meaning individuals with no first‐degree relatives with ASD, and excluded individuals with birth complications or with common medical or psychiatric disorders present in a first‐degree relative. A previous study of toddlers suggests that simplex ASD presents with significantly lower cognitive ability than multiplex ASD, and modest group differences in verbal–nonverbal discrepancies (small effect size), but no differences in autism severity [Dissanayake, Searles, Barbaro, Sadka, & Lawson, 2019]. Thus, these results may not generalize to the multiplex population.…”

Risk Factors and Pivotal Periods: Marital Status over 28 Years for Parents of Individuals with Autism

“…After age 13, we saw suggestions of a crossover effect, where divorces began to occur in those with siblings with autism. This finding, while it should be taken as preliminary, because of the limited sample size, could point to the resilience of multiplex families or the families need to maintain a stable household, at least until the children are older (Dissanayake et al, 2019).…”