Addiction is a complicated problem that often seems to run in families. The American Academy of Child and Adolescent Psychiatry states that children of alcoholics are four times as likely as other children to become alcoholics themselves. While many factors influence addiction, research suggests that certain genes are associated with an increased risk of addiction.
Twins and the Risk of Addiction
A Swedish study explored alcohol use in twins who were adopted and reared separately. The findings showed some environmental influence and strong biological risk factors for alcohol addiction.
- Those children who were exposed to alcoholism only through their adoptive families had a slightly higher incidence of alcoholism.
- Twins with alcoholic biological fathers had dramatically higher alcoholism rates whether or not alcoholism was present in the adoptive home.
Nicotine Addiction Risks
Everyone knows that tobacco is a highly addictive substance. It has now been discovered that certain genetic variations may cause some people to have a predisposition to tobacco addiction. A team from the Icelandic company deCODE Genetics has researched two areas of variation on chromosome 15, associated with increased risk of lung cancer. Their findings suggest that this variant may also makes people more addicted to tobacco once they start smoking.
The DRD2 Gene and Addiction Risk
The A1 allele of the DRD2 gene has been identified as increasing a person’s addiction risk. This genetic marker is more common in people addicted to alcohol or cocaine than in the general population. People with the A1 allele have lower levels of dopamine in their brains. Dopamine helps the brain experience feelings of pleasure and reward. Most addictive drugs cause an increase in dopamine production.
A test for the A1 genetic marker for addiction was created by Professor Ernest Noble, the director of the UCLA Alcohol Research Center. This test, which will cost about $35, is currently under development.
Other Genetic Findings
Many other genes are also associated with addiction risk. Research is often done on mice and other rodents: Their brain reward pathways function in much the same way as our human ones. When a mouse gene associated with addiction is discovered, scientists can then search for a human counterpart. Here are just a few of these exciting research findings:
- Mice lacking HTR1B, a serotonin receptor gene, are more attracted to cocaine and alcohol than those who have the gene.
- Mice with low neuropeptide Y levels are more likely to drink alcohol while those with higher levels tend to abstain.
- People born with two copies of the ALDH*2 gene variation rarely develop alcoholism.
- The protective gene CYP2A6, which causes nausea and dizziness from smoking, is more likely to occur in non-smokers than smokers.
DNA Testing for Addiction Risks
Genetic testing can not predict whether a person will definitely become an alcoholic or a drug addict. It can only point out the biological differences which might make a person more or less vulnerable to addiction if they use these substances. Advantages of genetic testing for addiction include:
- abstaining from alcohol, drugs or tobacco after testing positive for addiction risk
- early childhood intervention and education for those found to be at risk
- understanding addiction as a medical disease and reducing associated feelings of guilt and low self-esteem.
There are also some concerns raised by this type of genetic testing. Possible negative consequences of testing for addiction risk include:
- labeling individuals as addicts because of risk factor
- possible denial of employment
- possible loss or denial of health or life insurance
- genetic screening out of “undesirable” profiles during pregnancy by parents.
Environmental Causes of Addiction
Environment is a strong determining factor in addiction. Populations at risk for drug and alcohol addiction are often found in areas of high unemployment and poor economic conditions. These stressful situations can cause the brain to crave the dopamine producing escape of drugs and alcohol.
Experiments with rats and stress have supported this observation. Rats that were moved to a new cage and poked in the nose to induce stress all increased their consumption of alcohol and cocaine in response. Those rats bred to have a stronger drug response had long-term increased usage, while those bred for a weaker drug response only increased their consumption for a short time.
Gene Therapy and Reduced Alcohol Consumption in Rats
Understanding the genetic components of addiction may lead to successful future treatments. A study at Brookhaven National Labs explored the effect of gene therapy on the alcohol consumption of rats. Two groups of rats were studied, one that showed a genetic preference for drinking alcohol and the other that did not. Both groups of rats received a gene transfer which increased the level of dopamine brain receptors.
After the gene treatment:
- All rats decreased their alcohol preference and consumption.
- Rats in the alcohol-preferring group cut their alcohol consumption in half and had a 37 percent reduction in alcohol preference.
- Rats in the non-alcohol preferring group slightly decreased their alcohol consumption and preference.
- Results were most dramatic within the first few days of treatment and by day 20, both groups of rats returned to pre-treatment behavior.
American Family Physician Staff. (2006). Curbside consultation, at-home genetic tests. Retrieved September 17, 2008, from the American Family Physician Web site: http://www.aafp.org/afp/20060201/curbside.html.
BBC News Staff. (2008). Genetic link to smoking addiction. Retrieved September 17, 2008, from the BBC News Web site: http://news.bbc.co.uk/2/hi/health/7325971.stm.
Brookhaven National Laboratory News Staff. (2004). Gene therapy reduces drinking in rats with genetic predisposition. Retrieved September 17, 2008, from the Brookhaven National Laboratory News Web site: http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=04-47.
Helm, J. (2006). Myth of an “addict gene”. Retrieved September 17, 2008, from the AddictionInfo.org Web site: http://www.addictioninfo.org/articles/961/1/Myth-of-an-Addict-Gene/Page1.html.
Join Together Staff. (2006). Genetic test for addiction developed. Retrieved September 17, 2008, from the JoinTogether.org Web site: http://www.jointogether.org/news/headlines/inthenews/2006/genetic-test-for-addiction.html.
The University of Utah Staff. (2008). Genetics is an important factor in addiction. Retrieved September 17, 2008, from The University of Utah Web site: http://learn.genetics.utah.edu/content/addiction/genetics/.