Is the P3 amplitude reduction seen in externalizing psychopathology attributable to stimulus sequence effects?

P3 amplitude reduction (P3-AR) is associated with biological vulnerability to a spectrum of externalizing (EXT) disorders, such as conduct disorder, antisocial behavior, and substance use disorders. P3 amplitude, however, can be affected by the context within which it is measured, for example, by the position of the target in the sequence of stimuli during an oddball task. We hypothesized that EXT-related P3-AR may be due to attention or working memory deficits in EXT that would weaken these stimulus sequence effects. Using a community-based sample of adolescent males, we examined the relationship between P3 and EXT as a function of the number of standards preceding the target. Higher EXT was associated with significantly smaller P3 amplitude, regardless of the number of standards preceding the target. These results suggest that P3-AR in EXT does not vary as a function of stimulus sequence, further supporting P3-AR as an endophenotype for EXT disorders.