Our findings have implications for gene identification efforts. In recent years, numerous genome-wide association studies have attempted to identify specific genes or variants that are associated with alcohol-related phenotypes (Treutlein et al. 2009; Bierut et al. 2010; Edenberg et al. 2010; Lind et al. 2010; Baik et al. 2011; Heath et al. 2011; Kendler et al. 2011b; Schumann et al. 2011; Zuo et al. 2011, 2012; Agrawal et al. 2012; Frank et al. 2012; Wang et al. 2012), two of which specifically focused on alcohol consumption (Baik et al. 2011; Schumann et al. 2011). The results reported here indicate that the use of a sample population with a wide age range is more likely to result in high levels of genetic heterogeneity underlying liability to alcohol consumption, relative to a sample consisting entirely of mature adults (e.g. age 25 years or older), or a sample consisting entirely of late adolescents. In other words, including both mature adults and late adolescents/young adults in a sample could complicate gene-finding efforts due to the fact that different genetic factors are influential in different
