Studies of sufficiently large samples are currently being organized by the PGC Addictions group and GSCAN for large meta- and mega-analyses combining multiple GWAS datasets. Although these efforts will substantially increase the size of the study sample, they also introduce between-study heterogeneity, which could be mitigated by homogeneous subtype analysis. Latent class analysis was recently applied to an AD GWAS using the COGA sample (Wetherill et al., 2013), which identified a GWS association between “high risk” AD and a SNP in the NALCN gene. We have used cluster analysis to identify heritable, homogeneous subtypes of cocaine and opioid dependence (Bi et al., 2014; Sun et al., 2012; 2014). These methods may be useful in increasing statistical power in consortium-based analyses, including those focusing on AD.
