In addition to data that suggest the function of EC system is altered following chronic ethanol use and withdrawal, it is possible that allelic variation in the CNR1 gene may contribute to innate susceptibility to alcohol dependence. Unfortunately, the genetic association between CNR1 alleles and the susceptibility for alcohol dependence is clouded by conflicting datasets in most cases. Homozygosity for a CNR1 allele having five or more repeats of a microsatellite polymorphism is associated with a reduction of the P300 potential in the frontal lobes (Johnson et al., 1997), and reduced amplitude of the P300 wave is known to be a physiological marker that runs in families with a history of alcohol dependence and is associated with attentional processes (Begleiter et al., 1984). However, a companion study found no correlation between geneotype and self-reported alcohol-associated problems (Comings et al., 1997). In contrast, subsequent studies have found correlations between this allele and comorbidity between alcohol dependence and ADHD (Ponce et al., 2003) or psychopathy (Hoenicka et al., 2007), but at present the data still do not support a direct correlation between this allele and a susceptibility for alcohol dependence.
