Two previous reports from this laboratory suggest that risk status, presence of psychopathology, and age are critical determinants of P300 amplitude. Hill et al (1999) found high risk offspring to show a delay in acquiring age-appropriate P300. Presence of either an externalizing or internalizing disorder of childhood/adolescence altered the trajectory with lower amplitudes being seen across the trajectory of change in those having a childhood disorder. In a later report from this laboratory trajectories of visual P300 (P3b) were analyzed using data from annual assessments of 126 children and adolesents who were either at high risk for alcohol dependence because of their family loading of alcohol dependence or control subjects with a low risk because of absence of AD in first and second degree relatives (Hill and Shen, 2002). Using a mixture analysis approach, trajectory analysis of children with 5 or more assessments during childhood and adolescence revealed three patterns of visual P3b during development. Group I with the highest P300 amplitude showed relative stability over the 8–18 year age range (26%). Those in Group II exhibited higher amplitude in
