Brain development in healthy, hyperactive, and psychotic children.

S erious and chronic childhood psychiatric disorders have long been assumed to reflect relatively subtle abnormalities of brain development. Although diagnostic brain imaging is well established in pediatric neurology, it has not yet permitted quantitative assessment of brain abnormalities in children with psychiatric illnesses. Recent advances in brain magnetic resonance imaging (MRI) allow reliable, automated, quantitative measurement of multiple brain regions. The noninvasive nature of MRI also allows periodic rescanning for research purposes, making prospective longitudinal study of brain development feasible in large numbers of healthy children and those with psychiatric illness. Longitudinal MRI of the brain also makes possible the mapping of region-specific changes in brain volume over time.