That only a small fraction of the heritability of smoking quantity is detected by GWAS is a characteristic common to many other complex traits [13]. Preliminary estimates of the total amount of phenotypic variance explained by common SNPs (minor allele frequency >1%) [13], suggests that similar to other complex traits [13], [14], the percentage of genetic variance captured by GWAS chips is higher than that explained by the loci identified so far; this suggests that many of the signals that fail to reach genome-wide significance in current datasets are true signals.
