A number of clinical studies have investigated altered effects of alcohol in individuals with the G118 allele. For instance, in a sample of 38 moderate and heavy drinkers without a history of alcohol problems or quit attempts, it was shown that G118 allele-carriers reported higher feelings of intoxication, stimulation, sedation, and happiness compared to A118 allele-carriers. Subjects carrying the G118 allele were also three times more likely to report a family history of alcohol use (Ray and Hutchison, 2004). In male heavy drinkers, G118 allele-carriers showed automatic approach tendencies for alcohol and other appetitive stimuli, but not for generally positive or negative stimuli (Wiers et al., 2009) and reported greater alcohol craving in a cue-reactivity task (van den Wildenberg et al., 2007). A recent study investigating the involvement of A118G in adolescent alcohol misuse found that a higher percentage of G118 allele-carriers tested positive for an alcohol use disorder, and that the G118 allele was associated with increased self-reports of drinking in order to enhance positive affect (Miranda et al., 2009). Functionally, G118 allele-carriers have demonstrated an increased BOLD response
