Developmental precursors to adult disorder suggest that components of their causes operate in early life. Several birth cohort studies have relevant prospective data and are reporting results for schizophrenia and affective disorder. These studies suggest that developmental findings are not specific for schizophrenia, although the magnitude of effects tends to be greater compared with affective disorder. These findings are reviewed and some methodological issues discussed. Apparent lack of specificity may mask underlying unique mechanisms and causes. In terms of a future public health perspective involving prediction and prevention, a lack of specificity may be advantageous.