Characterization of Autistic Symptoms in Children Diagnosed with Autism Spectrum Disorder Before Age 2

Background:  By definition, the onset of Autism Spectrum Disorders (ASD) is before age 3. Despite increasing evidence that children can be diagnosed by age 2, few studies have focused on symptoms in very young children.

Objectives: To compare the clinical presentation of children diagnosed with ASD before age 2 to children diagnosed after 2
Methods: Retrospective chart review of 145 children, ages 1 to 4 presenting to a University Affiliated Program for initial multidisciplinary evaluation from 2003 to 2007, who received a diagnosis of ASD. Information reviewed included demographics, maternal age, medical, developmental and family histories, DSM-IV-TR symptom checklist, Childhood Autism Rating Scale (CARS), and the Bayley Scales. Statistical analysis included Chi-Square, T test, Mann Whitney and logistic regression.
Results: Of the 145, 41 were under 24 months (age range 18-48 months). Children diagnosed under 2 were more likely to have been born to younger mothers (29 +/- 5 vs 31.2 +/- 5 p=0.03). On the DSM-IV, children under 2 were more likely to show a lack of shared enjoyment (75% vs 48% p=0.009) and a preoccupation with parts of objects (61% vs 38% p=0.02), and less likely to present with stereotyped language (18% vs 48% p=0.002) and impairments in initiating and sustaining conversation (5% vs 30% p=0.01). These differences persisted after adjusting for level of maternal education, socioeconomic status, and cognitive level. There were no significant differences in autistic symptom severity (total CARS score) or in cognitive functioning (Bayley Scales).
Conclusions: Children diagnosed with ASD under 2 may not be more severe in terms of level of social impairment or cognitive impariment. They seem to present with a different pattern of autistic symptomatology. They are more likely to show a lack of shared enjoyment and demonstrate preoccupation with parts, and less likely to display stereotyped language and impairment in conversation than children diagnosed over 2.