Table 1.

Hierarchical Regression Analyses Demonstrating that Externalizing Vulnerability Accounts for Relations between Individual DSM-III-R Disorders and P300 Amplitude

	Unadjusted (step 1)			Adjusted (step 2)
Disorder	B	t	p	B	t	p
Alcohol dependence	−0.70	−4.20	<.001	0.02	0.08	.935
Drug dependence	−0.54	−3.18	.002	0.38	1.42	.156
Nicotine dependence	−0.82	−4.92	<.001	−0.37	−1.39	.164
Conduct disorder	−0.60	−3.59	<.001	−0.04	−0.17	.869
Adult Antisocial behavior	−0.75	−4.46	<.001	0.02	0.07	.947

Note. B is the raw regression coefficient obtained by regressing P300 amplitude, averaged across easy and hard target stimuli, on normalized symptom counts of each individual DSM disorder. It therefore reflects the decrease in P300 amplitude (in microvolts) associated with a standard deviation increase in symptoms of the relevant disorder. t is the test statistic for each B coefficient, and p its associated probability. The unadjusted coefficients were derived in the first step, in which disorder symptom count for each disorder was the sole predictor in the model. Adjusted coefficients were derived in the second step of each analysis, in which externalizing vulnerability score was added to the model as a second predictor, and therefore are adjusted for scores on this vulnerability factor.