Genome-wide arrays, such as Smokescreen, allow for imputation of common and rare genotypes using haplotype reference panels. Recent haplotype projects (e.g., the Haplotype Reference Consortium, which combines multiple cohorts including the 1000 Genomes Project) allow for more accurate imputation of less common and rare variants [63, 64]. The ability to genotype large numbers of study samples and impute more variants accurately, enables powerful meta-GWAS studies [65]. Additionally, genome-wide imputation allows for discovery of associations in regions not directly enriched for in the array design. This is important as meta-analysis consortia and multiple methods [51] identify additional addiction-related regions.
