Outcomes of Two-Year-Olds Enrolled in a Comprehensive Developmental Intervention

Background:

Early intervention for children with ASD has been a public priority.  However, there has been little empirical data available to judge the potential impact of early intervention on later functioning. 

Objectives:

To examine change in cognitive functioning over the course of one to six years after enrollment into an early intervention study in a group of 2-year-olds.

Methods:

Forty nine children who had entered an early intervention study between the ages of 24 and 33 months of age were tested one to six years after the onset of the intervention.  The children had received 10 hours per week of center-based intervention within a classroom setting for a period of 6 months.  Multiple intervention strategies were employed.  A comprehensive curriculum was used.  Weekly parent education sessions were provided, and monthly home visits were made to train parents on core intervention goals within the home.  Children were assessed with the Mullen Scales of Early Learning prior to entry into the intervention, at the end of the intervention, and at a 6-month post-intervention follow-up.   Sixteen of the children have thus far completed another follow-up assessment at 4, 5, 6, 7, and/or 8 years of age.  Six of these children completed the Mullen, and 10 completed the Stanford Binet V at the second follow-up assessment.  Dependent variables examined here included nonverbal functioning (Mullen Visual Reception T score; Stanford Binet Nonverbal IQ), verbal functioning (Mullen Receptive and Expressive T score; Stanford Binet Verbal IQ), and overall cognitive functioning (Mullen Early Learning Composite; Stanford Binet IQ).  Assessments were conducted by expert clinicians blind to intervention status and to children’s pre-intervention level of functioning.  Children were  tested in an unfamiliar environment with materials that were not used in the intervention classroom.

Results: Forty five percent of participants (n=22) made robust and sustained improvement from the pre-intervention to follow-up assessment that resulted in a shift from impaired functioning (scoring >1.5 sd below the mean) to functioning within normal limits (within 1 sd of the test mean).  For example, the mean Mullen Expressive Language T score improved from 26 (>2 sd below mean) to 46 (within 1 sd of the mean) in this group of robust responders.  Nonverbal functioning improved from impaired at the pre-intervention assessment (e.g., mean Mullen Visual Reception T score of 33, more than 1.5 sd below the test mean) to age-appropriate at follow-up (e.g., 44, within 1 sd of the mean).  Overall cognitive functioning (based on a mean of 100, sd=15) improved from a mean of 62 at pre-intervention to 96 at the follow-up assessment.  This represents improvement that was sustained at least 6 months after the intervention was terminated.  An additional five children made robust improvements in nonverbal or verbal functioning but their scores fell short of age-appropriate levels. Other children made improvement but did not reach age-appropriate levels on these measures.

Conclusions:

These findings indicate that comprehensive intervention initiated at 2 years of age for children with ASD may lay the foundation for important developmental gains in nonverbal and verbal aspects of functioning.