A rat study done at the University of Michigan found genetic markers that influence addiction.
People may ask why some people get addicted to cocaine after one try, while others will try it and be able to leave it alone. You may ask why some people are able to stay clean after rehab while others relapse. These questions may have a lot to do with the genetic factors that vary from person to person. Of course, we know that animal factors cannot explain all of the factors that lead to differences in addictions in human bodies, but the findings revealed information about the roles played by both inherited traits and addiction related changes in the brain.
The researches looked in rats' brains for the genetic instructions needed to make a key "pleasure receptor" called D2. It allows brain cells to receive signals sent by the brain chemical dopamine, or cocaine. They found that more addiction-prone rats had lower levels of D2 instructions to begin with when compared to the other rats, in an area of the brain known to play a major role in addiction.