Substance dependence and externalizing psychopathology in adolescent boys with small, average, or large P300 event-related potential amplitude

To determine if the P300 component of the event-related potential indexes r isk for substance use and related disorders, we presented a community sampl e of 377 16-18-year-old males a visual oddball task and selected 31 subject s with the smallest and 31 subjects with the largest P300 amplitudes. An ad ditional 31 subjects whose amplitudes fell in the middle of the amplitude d istribution were assigned to the average group. The small and average ampli tude groups were more likely to have alcohol dependence and more symptoms o f alcohol dependence than the large amplitude subjects. The small amplitude group had more symptoms of illicit drug dependence than the other groups. There was also a significantly larger proportion of subjects with externali zing disorders in the small amplitude group than in the large P300 group. T hese findings suggest that P300 amplitude may index a spectrum of risk for disinhibited psychopathology.