How do the characteristics of autism, Asperger syndrome, Rett syndrome, and childhood disintegrative disorder change with development?
There are a number of studies in which characteristics of A, RS, and CDD are compared in different age groups of children, adolescents, and/or adults (i.e., cross-sectional studies). However, there are few studies following the same children as they age so we have little evidence of how individuals actually change across the life-span (i.e., longitudinal studies). Asperger syndrome is a term that has been used frequently with adolescents and adults rather than with young children, so we have few cross-sectional or longitudinal data on AS. Several relatively large-scale, high quality, follow-up studies exist of psychometric (mental measurement test) data for autistic individuals. These studies have shown that the diagnosis of autism continues to apply as the children age and change, even after they have developed language. Longitudinal data are needed for all autism spectrum disorders in order to trace individuals’ paths of development. Such data would enable us to define the course of
