Symptoms of autism spectrum disorder and developmental delay in children with low mental age
Rebecca P. Thomas, Stephanie Milan, Letitia Naigles, Diana L. Robins, Marianne Barton, Lauren B. Adamson, Deborah Fein
Abstract
Objective: Autism spectrum disorder (ASD) in very young children with significant cognitive impairment is difficult to diagnose, depriving them of the earliest opportunities for autism-specific intervention. This study delineated specific symptoms in this group, compared to symptoms in children with Global Developmental Delay (GDD) and in ASD with milder developmental delays.Method: Autism Diagnostic Observation Schedule, 2nd Edition, Toddler Module revealed symptoms in three groups of toddlers, with mean ages of 17-20 months: (1) ASD and cognitive/language functioning below the 12-month level (ASD-MA < 12 mos; n = 28), (2) GDD (n = 27), and (3) ASD and cognitive/language functioning at or above the 12-month level (ASD–MA ≥ 12 mos; n = 29). Logistic regression models were fit to control for developmental level. Results: Items in all domains (social interaction, communication, repetitive movements) discriminated ASD-MA < 12 mos from GDD. The two ASD groups, matched for age but differing on developmental level, showed strikingly similar ASD symptomatology. Conclusion: ADOS-2 symptoms differentiated ASD-MA < 12 mos from GDD, after controlling for cognitive impairment. Symptoms in the two ASD groups were minimally related to developmental level. The ADOS-2 Toddler Module successfully captured ASD symptomatology even in children whose developmental level was below the recommended ADOS-2 cutoff of 12 months, which may increase their access to early ASD-specific intervention.