The evidence that heredity modulates the risk of nicotine addiction,3 led to the expectation that genetic advances would help us identify the genetic basis of substance use disorders in general and of nicotine addiction in particular. Unfortunately, the full potential of genome scans took longer to crystallize than expected, mainly due to the poor rate of replicability among the initial studies. But improvements in genome-wide association strategies kept eroding the barriers for establishing reliable connections (for example, small size effects, ill-defined endophenotypes, multiple test penalty, cost and so on).
