The Role Genetics Plays in Drug Addiction

While modern science allows research to dig down to the molecular level of addiction, experts have long connected it to family history. You don’t need a lot of genetic technology to see that addiction often runs in families.

This doesn’t mean that you’re destined to become addicted to drugs if your parents or siblings are. It simply means that you have an increased risk, which may be tied to genetics. Another important factor is environment. If you and your sibling develop a drug use disorder, it may be related to genetics but also the fact that you grew up in the same household with risk factors, like abuse or trauma.

Observations indicate that family history plays a role in addiction, but researchers have also proven it. Studies show that addictions range from moderately to highly heritable. Your risk of developing an addiction increases with the degree of your genetic relationship to an addict. In other words, your risk is higher if your parents struggle with addiction than if an aunt or cousin does.

That drug addiction is heritable implies that there are genes for it. Your parents may pass on genes to you that make you more likely to develop an addiction. Gene sequencing has led to incredible revelations about diseases, some of which are caused by a single mutation, or change in a gene.

Unfortunately, addiction is not that simple. There is no single gene or group of genes that cause this complicated disease. Researchers look for all kinds of genetic differences in people with drug addiction to determine underlying causes. These differences increase addiction risk. These are some examples:

• A gene called Mpdz may code for extra protein that leads to less severe withdrawal from certain drugs. If your withdrawal is milder, you are less likely to keep using to get relief, and therefore less likely to become addicted.
• Per1 and Per2 genes in animal studies can have variations in their sequences that trigger mice to consume more alcohol when stressed. If a person has this variation, they may be more likely to drink when under stress and to become dependent.
• Fruit flies missing a gene called moody are more sensitive to cocaine. Drug sensitivity increases the risk for addiction.
• Specific variations in the OPRM1 gene, which codes for a receptor for opioids, are more likely to occur in people with opioid addictions.
• DRD2 is a gene that in a certain form occurs more often in people addicted to cocaine, opioids, and alcohol. Researchers believe it’s related to the brain’s reward pathway.

These are just a few of the many genetic variations that contribute to addiction risk. None of these causes addiction to drugs, but the more you have, the greater your risk.

Epigenetics is an area of research that looks at the regulation and expression of genes. Environmental factors and lifestyle choices can actually change the action of your genes and the proteins produced based on those genes. These things don’t change the sequence of your genes, only how they are expressed.

In terms of addiction, studies find that some epigenetic changes impact your risk of using or becoming addicted to drugs. Stress, for instance, triggers the release of hormones that can change gene expression in brain cells. These changes can make you more susceptible to using drugs or to relapsing in recovery.

Ordinary stress is not a huge risk factor, but researchers have found that severe stress, or childhood trauma, significantly impacts addiction risk because of epigenetic changes. In one study, children who lost their parents had a parent diagnosed with cancer, or who witnessed domestic abuse, were two times more likely to develop a drug addiction.

Drugs themselves can also produce epigenetic changes. Cocaine use increases the production of certain proteins as coded by specific genes. These proteins, related to substance abuse, have been seen to correlate with increased drug use.

The environment in which you grow up and live as an adult can impact your risk for drug addiction through these epigenetic changes. Together with specific genes and family history, the contribution of genetics is significant.

Even without considering epigenetics, environment matters. For example, a study of people in China, Japan, and other Asian countries found that many people in this population have a gene that protects against alcohol addiction. It interferes with the metabolism of alcohol, making drinking even a small amount unpleasant.

In spite of this protective gene common in the population, researchers found that alcohol abuse rose significantly in Japan between 1979 and 1992. This coincided with a period of time in which a culture of heavy drinking among businessmen developed. Many men found themselves in an environment that promoted and rewarded drinking, which changed their behaviors.