The specific aims of this study are twofold: 1) to define and concurrently describe sub-groups of ADHD according to DSM-IV criteria based on parent and teacher report measures at 8 years of age. 2) to identify the factors from pregnancy through infancy, preschool and early school years that predict ADHD and test whether these are similar or different for three subtypes of ADHD and for boths sexes.

The proposed study will thus identify the affected children and provide an empirically tested model of the relevant environmental factors that increase the risk for or protect against ADHD. This information, highly relevant for developing effective preventative models. will furthermore provide the basis for future groundbreaking research at the molecular level, testing for gene-environment interactions (to be applied for separately). This will be possible due to recent developments in pinpointing promising candidate genes (Zametkin et al., 2001) and the fact that ALSPAC has DNA on 10,000 of the children and most of their mothers. Samples of paternal DNA are planned for the future.