To determine if the P300 component of the event-related
potential indexes risk for substance use and related disorders,
we presented a community sample of 377 16–18-year-old
males a visual oddball task and selected 31 subjects with
the smallest and 31 subjects with the largest P300 amplitudes.
An additional 31 subjects whose amplitudes fell in the
middle of the amplitude distribution were assigned to the
average group. The small and average amplitude groups were
more likely to have alcohol dependence and more symptoms
of 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 externalizing
disorders in the small amplitude group than in the large
P300 group. These findings suggest that P300 amplitude
may index a spectrum of risk for disinhibited psychopathology.