The name is absent

Autism prodrome 32 of 89

with samples of older children and adults, might however be consistent with
continuity in organization of the cortical system from early infancy throughout
childhood development - identifying at least a possible candidate neuropathological
process, even its cause is not yet known. Whether such neuropathological processes
will ever be seen as reliable and universal enough in relation to ASD outcomes to be
candidate prodromal signs will require a considerable body of further research.
Furthermore, the degree to which any of these possible brain markers (abnormal
connectivity; abnormal growth trajectory) will be specific to ASDs is unclear as they
are also emerging as putative biomarkers in relation to many other
neurodevelopmental and neuropsychiatric outcomes (e.g. ADHD: Castellanos et al.,
2002; Schizophrenia: Bluhm et al., 2009) and their specificity to ASD has not yet
been adequately tested. However, the notion that a neurodevelopmental perturbation
might herald and precede the emergence of symptoms of ASD resonates at behavioral
level with the long-recognized phenomenon of developmental regression or ‘setback’.
Is regression part of the prodrome in ASDs?

According to studies reliant on retrospective parental report, regression or loss
of skills is seen in between 15% and 30% of cases in different clinical and population
samples with the most common timing being between 12 and 24 months of age (Baird
et al., 2008; Fombonne & Chakrabarti, 2001; Lord, Shulman, & DiLavore, 2004;
Luyster et al., 2005; Richler et al., 2006; see Young & Ozonoff, in press, for a
review). This is also around the time that the earliest symptoms of ASD emerge in
many children and both the retrospective videotape analysis studies (e.g., Werner &
Dawson, 2005) and the ‘at risk’ sibling studies (Landa & Garrett-Mayer, 2006; Landa
et al., 2007) reviewed above have shown prospective evidence of loss of skills or
stasis. The speculation surrounding whether there may be a link between the apparent

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