Autism is a complex disorder of development and represents a subclass of Pervasive Developmental Disorder (PDD). It is crucial to identify early biological and behavioral risk factors for PDD, as well as for its severity, since there is evidence that early intervention is effective in improving long-term outcome, especially among more mildly affected cases. Researchers have attempted to identify early signs by studying "baby sibs" - infant siblings of children with autism (10-fold increased risk for developing PDD). Another group at risk is infants with obstetrical/neonatal complications (3-4 fold risk).
The Behavioral Assessment and Research group in the Dept. of Psychology has diagnosed with PDD approximately 1/3 of the 2% suspect cases who had been studied intensively by the Infant Development group. Data will be presented on the behavioral characteristics of this subgroup of PDD, how they compare with typically referred cases, and the relations between early physical and neurobehavioral measures with later dimensional measures of PDD traits and adaptive skills measured at an average age of 4 years in this group and non-PDD diagnosed cases.
Infants were evaluated in the NICU prior to discharge and followed every 3 months between 1 and 25 months (post term age). Infancy measures included anthropometric measures obtained at birth, measures of degree of neurological insult, and a variety of behavioral and cognitive assessments. Behavioral diagnostic assessments when children were, on average, 4 years of age, included the Autism Diagnostic Observation Schedule-G (ADOS-G), Vineland Adaptive Behavior Scales, and parent and teacher ratings using the PDD Behavior Inventory (PDDBI), an age-standardized dimensional measure of PDD traits.
Preliminary data indicate moderate to strong associations between birth measures (e.g., body length, birth weight, visual asymmetry) and neurobehavioral assessments (e.g., atypical looking preferences to higher amounts of stimulation) performed before 12 months of age with a variety of later PDDBI domain scores including: SENSORY (sensory seeking-type behaviors); AROUSE (hyper- and hypoactivity); SOCIAL DISCREPANCY Composite (a measure of social competence); AUTISM Composite (a measure of autism severity); REPRIT Composite (a measure of classic autism traits); and AWP Composite (a measure of autistic and non-specific behavioral traits) in the PDD group. The smaller the infant, the greater the SENSORY and AROUSE scores. Preference for high frequency visual stimulation at 4 months was strongly correlated with later PDDBI measures of autism severity and early measures of visual asymmetry modulate this effect.
NICU infants are at high risk for PDD, in addition to other developmental disabilities. These data indicate that early physical and neurobehavioral measures suggest associations to later PDD traits. The patterns thus far, although specific to these NICU infants, appear to fall between those for CNS-injured and cocaine-exposed infants.