Longitudinal follow up of offspring from families presents a number of challenges for data analysis. The present analysis was based on offspring from either high or low risk families who were invited to participate if they were between the ages of 8–18 years at initial assessment. Although the majority of subjects were between the ages of 8–12 years at initial assessment, nevertheless all cohorts were not at the same age at each wave. The choice of analytic methods for trajectory analysis can either be based on repeated observations (waves) or by age. If one uses a wave approach in which all offspring are studied by wave irrespective of age, considerable age variation is introduced but the number of previous times experiencing the assessment paradigm is controlled. For the present analyses, all individuals of a given age were analyzed with repeated measures increasing by age. A limitation of this method is that some individuals might have varying number of previous assessments so that previous experience doing the ERP tasks might influence the measured results. Although this is a limitation, it may
