Autism prodrome 13 of 89
develop ASDs later on, after showing these early markers, are required in order to
specify which of these behaviors are or are not necessary and/or sufficient to be
included in the prodrome/s of ASDs (the ‘specificity’ question outlined above). Some
of the prospective studies which include large cohorts of both typically developing
children and groups of children at risk for ASD offer some of this much needed
information.
-------------------Table 1 about here-------------------
What can we learn about the prodrome of ASDs from prospective
screening studies?
At the beginning of the 1990s, Baron-Cohen and colleagues set out to develop a
prospective screening instrument for ASDs. In contrast to the rating scales available at
the time that measured severity of autism symptoms but were designed to assess older
clinically referred samples rather than screen a population (e.g. ABC: Autism
Behavior Checklist; Krug, Arick, & Almond, 1980; CARS: Childhood Autism Rating
Scale; Schopler, Reichler, DeVellis, & Daly, 1980); the intention was to develop a
measure of the early, emerging signs of the disorder that would attempt to identify
cases before clinically significant symptoms had been recognized by parents or
professionals. Drawing on evidence that impairments in social orienting behaviors
(specifically joint attention behaviors) and pretend play differentiated preschool
children with ASD from children with general developmental delay (Baron-Cohen,
1987, 1993; Mundy, 1995; Sigman, 1998), a new instrument was developed. The
CHAT (CHecklist for Autism in Toddlers) was designed to prospectively identify
autism at 18 months of age. This age was chosen as an appropriate screen "window"
(Aylward, 1997) because joint attention and pretend play typically emerge at this time
in normal development. The CHAT assesses simple pretend play (appropriate use of a