Original articleWhen Is the Brain Enlarged in Autism? A Meta-Analysis of All Brain Size Reports
Section snippets
Methods and Materials
MRI, HC, and post-mortem studies were identified through literature searches on Medline, PsycInfo, and Web of Science. Brain weight data were requested from authors if the weights were not reported in the paper. Information on additional autopsy cases was provided by the Autism Tissue Program.
Qualitative Changes in Brain Size with Age
To assess qualitative changes in brain size differences between autism and control groups from birth to adulthood, HC and MRI percent differences were plotted by mean age of study group and a curve was fitted to these data. The equation with the least squares and highest correlation with the %Diff data is given below:
This fit accounts for 78.1% of the variance in the %Diff data (r = .88). As seen from the plot of this line in figure 1, the data reveal the
Discussion
Several studies have identified the presence of brain enlargement during childhood in autism (Aylward et al 2002; Courchesne et al 2001; Sparks et al 2002). According to a recent study, this brain enlargement may begin as early as the first year of life (Courchesne et al 2003). The present study, using all data available from the autism brain size literature, shows the entire developmental course of brain enlargement in autism and reveals that it is time-delimited to the first 2–4 years of
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