29608
Initial Severity of Autism Symptoms Moderates the Effect of Intensity on Expressive Communication in Children with ASD
When intensity levels have been compared in other populations, differences between two intensity levels of the same treatment tended to vary by characteristics of the children prior to treatment (i.e., moderators).
Objectives:
To determine whether initial severity of autism moderates the effect of intensity of treatment on expressive communication.
Methods:
The measure of expressive communication was derived from 12 monthly six-minute semi-structured communication samples administered by an examiner who was blind to intensity group assignment using toys not used in the treatment sessions. These sessions were coded by an observer who was blind to intensity group using a timed event sampling method. The metric from this procedure was the weighted frequency of intentional communication. Weights varying from 1 to 3 were assigned for nonverbal, single word, and multi-word communication acts, respectively. The measure of ASD severity was the calibrated severity score from the ADOS.
The mixed level model of growth in expressive communication was described by Dr. Rogers. Slope was used as the parameter of interest.
Results:
Time was centered at study entry; thus, intercept could be interpreted at level at study entry. There were a nonsignificant interaction between ASD severity and Intensity Group on the intercept. There was significant gain in weighted frequency of intentional communication in both intensity-level groups, but no main effect of intensity level.
There was an interaction between autism severity and intensity level on weighted frequency of intentional communication growth rate (pseudo R square change = .07; Cohen’s d = .55) with higher intensity affecting communication more than lower intensity in the mildly affected children only (CCS 3 – 7).
Conclusions:
This is the first study to show that intensity of treatment affects only mild to moderately affected children with ASD. This is analogous to a finding Dr. Rogers reported on: the least affected children benefited from more hours of treatment per week. Additionally, this study showed that a particular method of briefly assessing communication called individual growth and development index (IGDI, Carta, Greenwood, Walker, & Buzhardt, 2010) is sensitive to treatment effects (a type of validity).