Subject demographics.

All values represent either number of subjects or the mean±SEM.
aRepresents years of education completed. Completion of GED scored as 12 years. The groups were significantly different: t (31)  = 3.20, p = 0.003.
bCocaine use frequency is presented in three formats: (top) number of days used over the past 30 days; (middle) number of years used (lifetime); and (bottom) the Kreek-McHugh-Schluger-Kellogg scale (KMSK, [72]), a rating designed to quantify drug use. The KMSK scale assesses the frequency, amount, and duration of drug use during the individual's period of heaviest consumption.
cLifetime total alcohol use in kg, estimated from years of use, weekly frequency of drinking, drinks per occasion, and type of alcohol consumed. The groups were trend significantly different: Wilcoxon Two-Sample z = 1.81, p = 0.071.
dNumber of subjects who reported current smoking. Intake data did not contain consistent frequency of use levels across subjects. The groups were significantly different, χ2 = 13.60, p<0.001.
eNumber of subjects meeting DSM-IV criteria for past or present abuse or dependence of a drug other than cocaine.
fTwo subjects had present alcohol abuse only. Two other subjects had past alcohol abuse only. None of the subjects had past or present alcohol dependence.
gStimulant other than cocaine (e.g., amphetamine); one subject had past abuse and dependence, one had past abuse.