A combination of many factors including genetics, environment and behavior influence a person's addiction risk, making it an incredibly complicated disease .

Searching among all of our 20,000 or so genes for a few that are involved in a complex disease can
be quite costly and time consuming. That is why researchers often use what they and others know about
a disease to narrow their focus down to a smaller number of "candidate genes".

Learn more at : Learn Genetics : The Addiction Genes