The researchers found that the presence of RASGRF2 in their sample populations went from 6% to 14% and 9.5% to 34% when comparing controls to chronic drug abuse

The researchers found that the presence of RASGRF2 in their sample populations went from 6% to 14% and 9.5% to 34% when comparing controls to chronic drug abusers. So this means that addiction is a complex, multi-factor condition, and these researchers may have identified another factor. People with this gene may be predisposed to addictive behaviors but not behave that way for any number of environmental or other reasons; likewise, people without the gene may still develop addictive behaviors. The researchers didn't study rats or dogs, so there isn't much in the way of evidence for this gene's presence in those species.