Language Development in High-Familial Risk Infants Who Go on to Have Autism or Language Delay

Background:  Infant-sibling studies have indicated that infants who develop ASD exhibit emerging delays in language skills around 12 months that become more pronounced by 24 months. Toddlers with ASD tend to show balanced receptive/expressive profiles, whereas typically developing toddlers show a receptive language advantage (i.e., higher receptive than expressive scores; Hudry et al, 2014). However, language outcomes for unaffected siblings have been inconsistent (Landa et al., 2006; Charman et al., 2016). It is not clear if unaffected siblings show language delay and a receptive language advantage.

Objectives:  This study included two main objectives: (1) to compare the language development of two groups of high-risk infants, those who go on to have ASD and those without ASD who demonstrate language delay, and (2) to determine if infants with ASD or language delay display normative patterns of receptive advantage.

Methods: Infants at high and low familial risk for ASD were assessed longitudinally at ages 6, 12, and 24 months. Inclusion criteria included the completion of least two assessments and diagnostic outcome at 24-months (N=525).

At each visit, infants were assessed using the Mullen Scales of Early Learning (MSEL). Verbal developmental quotients (VDQ) were calculated from receptive and expressive subscales. Receptive advantage scores were generated by computing receptive-expressive difference scores (Hudry et al., 2014). Positive values indicate higher receptive than expressive language scores.

Eighty-six infants met clinical best-estimate criteria for ASD (HR-ASD, 77% male) at age 24 months. The remaining high-risk infants without ASD were then classified by language delay. Criteria for LD was a t-score <35 on either the MSEL receptive or expressive language subscale (>1.5 SD below population mean), in accordance with standard measures (Northrup & Iverson, 2015). Of these high-risk infants, 41 met criteria for language delay (HR-LD, 65% male) and 255 did not meet criteria for either ASD or LD (HR-neg, 54% male). An additional 143 low-risk control infants (LR-neg, 58% male) did not meet criteria for ASD or language delay. Dependent variables included VDQ, MSEL expressive and receptive t-scores, and receptive advantage score. All models included the effects of group, time, group*time, and were covaried for sex, NVDQ, and maternal education.

Results:  Longitudinal mixed models indicated that trajectories of language development differed across groups for VDQ, t-scores, and receptive advantage (p<.005). Follow-up cross-sectional analyses indicated that groups did not differ in VDQ at 6-months, however at 12 and 24-months group differences were evident, with HR-ASD and HR-LD < HR-neg < LR-neg (Table 1). Receptive advantage scores did not differ by groups at 6- or 12-months; however, at 24-months the HR-ASD group displayed lower receptive advantage scores than all other groups.

Conclusions:  Our results indicate that high-risk toddlers who have ASD and toddlers who display language delay both show lower language scores at 12-months when compared to peers. Interestingly, toddlers with language delay displayed the expected receptive advantage profile at 24-months, whereas toddlers with ASD displayed a more balanced profile. These receptive advantage results may reflect an aberrant process specific to ASD that becomes apparent in the second year of life.