drinking and problems among subjects with lower LR’s (Heath et al., 1999; Rodriguez et al., 1993; Schuckit and Smith, 2000; Volavka et al., 1996), even after controlling for the usual drinking pattern prior to the alcohol challenge (Schuckit, 2002; Trim et al., submitted). However, alcohol challenges can only be used with individuals old enough to give informed consent (i.e., ∃ age 18), and, therefore, are often carried out five or more years after the onset of drinking. Despite matching higher and lower risk subjects on drinking histories, this delay raises the question of whether the observed LR reflects early sensitivity to alcohol or differences among groups regarding the development of acquired tolerance. Another problem with these challenges is their high cost which limits the number of subjects who can be incorporated into a research protocol.
