While candidate gene studies allow the investigator to focus on a specific gene with high resolution, they preclude the possibility of gene discovery. Genomewide association studies, where SNPs are used to map the entire genome with considerable density, combine the resolution of gene association studies with the exploratory capabilities of linkage. For SUDs, such studies are fairly recent and while there are, currently, no published reports in adolescent populations, several large studies of adult samples have identified possible genetic influences on smoking85, alcohol dependence86 and most recently, cannabis dependence87.
