One preliminary example of how genetic markers have been associated with different phenotypes across developmental stages is found in studies of the gamma aminobutyric acid receptor alpha 2 (GABRA2) gene. Markers in this gene have been consistently associated with alcohol use disorder in adults (Edenberg et al., 2004, Bierut et al., 2010) but not in adolescents (Dick et al., 2006, Sakai et al., 2010). Instead, during adolescence these markers have been associated with externalizing disorders such as conduct disorder (Dick et al., 2006; Dick et al., 2009; Sakai et al., 2010; Melroy et al., 2014). This demonstrates the heterotypic continuity associated with GABRA2 and the need to test post-GWAS markers in younger samples to understand how risk unfolds across development.
