Susceptibility Does Not Mean Inevitability
When scientists look for "addiction genes," what they are really looking for are biological differences that may make someone more or less vulnerable to addiction. It may be harder for people with certain genes to quit once they start. Or they may experience more severe withdrawal symptoms if they try to quit.
Factors that make it harder to become addicted also may be genetic. For example, someone may feel sick from a drug that makes other people feel good. But someone's genetic makeup will never doom them to inevitably become an addict. Remember, environment makes up a large part of addiction risk.