low parental monitoring (Dick et al., 2009). Other studies report that the minor allele is the risk-increasing allele (Fehr et al., 2006); however, we note that inconsistency in the identity of the risk-increasing allele for GABRA2 may be attributable to high heterozygosity, genotyping methods adopted across different labs (e.g., genomic strand differences), and variation in allele frequency across populations. For example, previous reports have found differential allelic effects for GABRA2 and nicotine dependence across racial/ethnic groups (Beuten et al., 2005), underscoring the importance of attending to the direction of genetic effects across diverse samples.
