These design challenges have been addressed, to some extent, by population-based prospective studies, which assess a birth cohort at multiple timepoints during childhood, adolescence, and young adulthood. Interestingly, however, data on the trajectory of intellectual functioning from several extant birth cohort studies do not converge. In some studies, children who eventually develop schizophrenia exhibit significant declines in intellectual skills (4), whereas in other studies, preschizophrenic children displayed static cognitive deficits during childhood (5). In this issue of the Journal, the article by Reichenberg and colleagues (6) takes this unresolved question head-on. Reichenberg et al. investigated the cognitive trajectories of a cohort of children born in 1972—73 in Dunedin, New Zealand, who were followed from birth to age 32. The data reported here are drawn from IQ assessments at four timepoints between the ages of 7 — 13 years. In order to determine the specificity of cognitive trajectories in preschizophrenic children, their development was compared to both healthy comparison children and children who eventually were diagnosed with recurrent depression. Whereas several other prospective cohort studies have used composite indicators of intellectual function (5), this study disaggregated IQ into multiple cognitive functions, including verbal reasoning, visuospatial problem solving, working memory, attention, and processing speed. Moreover, standardized, reliable mental health assessments were built into this cohort study, thus overcoming potential limitations of several other studies that relied on public mental health registries to identify patients on whom childhood developmental data also existed.