To investigate the relationship between P3 amplitude, each TF component, and externalizing disorders, subjects were divided into diagnostic groups based on their clinical diagnoses at study intake. Diagnostic groups were: conduct disorder (CD; N=184), attention-deficit/hyperactivity disorder (ADHD; N=45), oppositional defiant disorder (ODD; N=87), nicotine dependence (ND; N=68), alcohol abuse/dependence (AAD; N=95), and illicit drug abuse/dependence (DAD; N=35; which included amphetamines, cannabis, cocaine, hallucinogens, inhalants, opioids, PCP, and sedatives). Group assignment was made without consideration of possible comorbid diagnoses, producing representative samples of individuals with each diagnosis. A control group was also formed, composed of those 71 subjects who were free of any psychiatric disorders and free of paternal risk for substance use disorders (i.e. their father and his first-degree male relatives had no history of serious substance abuse problems, determined by structured interviews with subjects’ fathers and mothers using the Substance Abuse Module, and a composite interview from the Family History-Research Diagnostic Criteria (Andreasen, Endicott, Spitzer, & Winokur, 1977) and Family Informant Schedule and Criteria (Mannuzza, Fyer, Endicott, & Klein, 1985)).
