How do genetic variations influence a person becoming addicted?

Genetic variations can increase the likelihood of a person becoming addicted. Many alcoholics have a genetic alteration that reduces their number of dopamine receptors, lowering the brain's ability to perceive dopamine. This gene variation is called the D2R2 allele. Although 25 percent of the general population has this allele, 75 percent of severe alcoholics have it, as do 50-80 percent of those addicted to drugs. The D2R2 allele is also linked to depression and attention deficit disorder (ADD). Fifty percent of those who struggle with ADD also struggle with substance abuse. Medications given for ADD or attention-deficit hyperactivity disorder (ADHD) raise dopamine levels. Exercise is also a very effective way of raising dopamine levels.

If you have a genetic predisposition to addiction, it does not necessarily mean that you will have a problem with addiction. What it does mean is that if you are exposed to certain addictive substances or behaviors, you will run a higher risk of becoming addicted than would someone who didn't have that gene. Likewise, if you don't have any genetic predisposition, it certainly does not mean you cannot become addicted; it simply decreases the likelihood.

Studies of twins and families that are prone to addiction suggest that about 50% of the risk for drug addiction is genetically based. The genetic ties to behavioral expressions of addiction have not been studied as thoroughly, but there is evidence that genes play a similar role in gambling disorders. A few reports even hint at a genetic link to compulsive shopping. More importantly, experts in the field propose that there is a genetic "load" or constellation of genes that predisposes people to addiction, but not necessarily to a specific type of addiction. In other words, the same genes that drive substance dependence might also drive compulsive shopping and compulsive gambling.