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Alcoholism and Genetics: Should I Just Give Up and Keep Drinking?
Alcohol and Genetics
Is there a link between alcoholism and genetics, or is it just a matter of growing up in a household with prevalent alcohol use? The existence of some sort of a link is clear across the board, both in general and scientific literature. There is however a discrepancy between various articles and research, over how strong the link is and whether, or where, it has truly been placed on the human genome.
Difficulty in Separating the Facts
The relationship between inheritance and alcoholism is extremely difficult to positively confirm because, in general, a child that has inherited an “alcoholism gene” would grow up in a household with a parent exhibiting that gene, i.e. exhibiting alcoholism. Certainly growing up in a house with one or more alcoholic adults does not discourage children from drinking themselves. The environment, itself, could even influence the likelihood of a child to drink in more than one way. Its influences could include: the greater prevalence of alcohol, the acceptance of the use of alcohol in that home/environment, or even difficult life situations that turned a parent to drinking, that also influence the child.
Additionally, there are so many qualities and traits that have a positive correlation to alcoholism, separating them out and connecting them each to genes is that much more difficult. Traits as broad as the ability to hold a higher than average amount of alcohol and even the simple susceptibility to addiction could all theoretically affect likeliness to develop an addiction to alcohol. Researchers on the topic have identified over 3,800 individual genes with a link to alcoholism (http://www.geneticsandhealth.com/2006/04/19/genetics-of-alcohol-drinking/).
Just How Strong is the Correlation?
One of the most notable discrepancies between general and scientific literature is in the strength of the correlation. An article on HealTalk.com confidently boasts that while genetics make up approximately 60% of the risk of developing alcoholism, the environment makes up 40%, and that alcoholism is still very much a conscious decision (http://www.healtalk.com/public/54.shtml). As the article gives no real explanation of how these figures were acquired, or from what, its emphasis moves on to “proactive problem solving” in alcohol abuse reduction and is surrounded by ads for alcohol abuse rehab and intervention centers.
In a less advertisement focused, controlled study, of the offspring of twins, researchers establish that the exposure to alcoholism from a parent actually had no statistical significance. Once genetics are controlled for, the environment has very little affect. When comparing alcoholics and non-alcoholics, there is a greater chance of offspring of alcoholics developing an addiction (0.29 to 0.24), but once unconfounded, and controlling for genetics, the disparity is insignificant. The disparity was found insignificant by comparing the offspring to their parents’ twin siblings (i.e. identical DNA to parent), where the true affect of the genetic factors, outside of the alcohol-influenced environment could be accounted for (Slutske, et al, 2008). This study, from the Journal of Abnormal Psychology, therefore gives a much greater weight to genetics, as clearly 40% would be a significant affect.
Furthermore, in a study done in the UK and Germany, a genetic link was proven by showing that an MMP-3 genotype (which is linked to alcoholism) was in Hardy-Weinberg Equilibrium-- a classical Mendelian form of genetics (2008).
A more general article, using an interactionist perspective, (whose scientific basis lies about half way between that of the two fore mentioned articles), argues that there are only actually a dozen genes that have been specifically linked to alcoholism (Nurnberger 2008). Furthermore, while Slutske et al (2008) found no significant difference in the likelihood of offspring to have alcoholism whether it was a part of their environment or not, Nurnberger (2008) states that genes only modestly affect development of alcohol. While the article does point out the difficulty in separating out the numerous genetic and environmental relationships to alcohol, of the above articles, only the controlled studies truly address specific, and significant, confounding variables. The articles from Scientific American and HealthTalk.com use models that give more regard to the environment. Nurnberger (2008), unlike the HealthTalk.com article, is not trying to sell a product, but give an analysis of the subject from a wider point of view than straight scientific research.
Narrowing Down the Positive Correlation to a Specific Gene
Researchers, in general use two techniques to find a relationship between a gene and alcoholism. The first, and most commonly used in scientific studies, is the Candidate Gene Approach, and involves finding a specific gene with a known physiology that is believed to be a risk for the development of an alcohol addiction, then testing individuals for that gene (http://alcoholism.about.com/cs/alerts/l/blnaa18.htm). For example, a study by Hildreth (2008), did an analysis of glutamatergic neurotransmission genes in relation to alcohol dependence, and found an association between alcohol dependence and the NR2A gene. Also using the Candidate Gene Approach, researchers used the bitter-taste receptor and worked backwards towards a gene (hTAS2R16), to shown its influence in alcohol dependence (Hinrichs et al, 2006). In research they found this gene, which encodes a taste receptor for B-glucopyranosides, had a very significant correlation (P = 0.00018) to alcohol dependence.
Using the second method, geneticists can discover genes with a relationship to alcoholism, by scanning the human genome and linking genes to phenotypes one at a time, eventually coming across a gene that would show a link to this particular phenotype (http://alcoholism.about.com/cs/alerts/l/blnaa18.htm). The former practice is obviously more reasonable and more common.
These two methods have located thousands of genotypes and other traits with a linkage to alcoholism-
Dopamine D2 Receptor- more commonly found in alcoholics (http://alcoholism.about.com/cs/alerts/l/blnaa18.htm)
ALDH1- slower alcohol metabolism, resulting in decreased susceptibility to alcohol addiction; most commonly in Asian populations (Nurnberger et al)
ADH genes (linked)- increased risk of alcoholism as a result of metabolism, most common in those of European decent (Nurnberger et al)
GABA receptor genes (http://alcoholism.about.com/cs/genetics/a/bluwa040114.htm0
Thousands of Others
Other heritable factors:
Body’s Rate of Metabolism of Alcohol
Possibility of Multiple “Alcoholism Genes” being linked on a single chromosome and being inherited together (http://alcoholism.about.com/cs/alerts/l/blnaa18.htm)
Dopaminergic neurotransmitters- stimulant effects
GABAergic neurotransmitters- sedative effects (http://www.medicalnewstoday.com/articles/5931.php)
Thousands of others
So, Should I give up and Just Keep Drinking?
While the scientific research on the relationship between alcoholism and genetics is far more conclusive and persuasive than general literature, it uses an organismic approach that is incomplete. While research studies take into account confounding variables and offer much better evidence, they give no real solutions. Thousands of genes have been linked to alcoholism, alcohol dependence, etc., but no solutions are ever given from a biological standpoint. While HealthTalk.com may be making an overstatement in arguing that 40% of the risk of alcoholism is environmental, the website has countless links to treatments and talks about the importance of prevention, especially in the case of the “alcohol gene” where one would be at a much greater risk.
Alcoholism; Research on alcoholism reported by scientists at University of Bern. (2008, July). Genomics & Genetics Weekly,8. Retrieved October 10, 2008, from Health Module database. (Document ID: 1504082291).
Anthony L Hinrichs, Jen C Wang, Bernd Bufe, Jennifer M Kwon, et al. (2006). Functional Variant in a Bitter-Taste Receptor (hTAS2R16) Influences Risk of Alcohol Dependence. American Journal of Human Genetics, 78(1), 103-11. Retrieved October 10, 2008, from Sciences Module database. (Document ID: 961007931).
Carolyn J Hildreth (2008). Systematic Analysis of Glutamatergic Neurotransmission Genes in Alcohol Dependence and Adolescent Risky Drinking Behavior. JAMA, 300(12), 1396. Retrieved October 10, 2008, from Health Module database. (Document ID: 1569176881).
Fromme, Kim (2004, Feb 16). Alcoholism risk related to genetics, alcohol sensitivity, and behavior. Retrieved October 8, 2008, from Medical News Today Web site: http://www.medicalnewstoday.com/articles/5931.php
John I Nurnberger Jr, Laura Jean Bierut. (2007, April). SEEKING THE CONNECTIONS: ALCOHOLISM AND OUR GENES. Scientific American, 296(4), 46-53. Retrieved October 10, 2008, from Research Library Core database. (Document ID: 1243348491).
Lei, Hsien Hsien (2006, April 19). Genetics of alcohol drinking. Retrieved October 8, 2008, from Genetics and Health Web site: http://www.geneticsandhealth.com/2006/04/19/genetics-of-alcohol-drinking/
NIAAA, The genetics of alcoholism: Alcohol alert. Retrieved October 9, 2008, from About.com Web site: http://alcoholism.about.com/cs/alerts/l/blnaa18.htm
Soinski, Denny (2008, June 24). Is alcoholism caused by genetics or by the environment?. Retrieved October 8, 2008, from Heal Talk Web site: http://www.healtalk.com/public/54.shtml
Wendy S Slutske, Brian M D'Onofrio, Eric Turkheimer, Robert E Emery, K Paige Harden, Andrew C Heath, Nicholas G Martin. (2008). Searching for an Environmental Effect of Parental Alcoholism on Offspring Alcohol Use Disorder: A Genetically Informed Study of Children of Alcoholics. Journal of Abnormal Psychology, 117(3), 534. Retrieved October 10, 2008, from Research Library Core database. (Document ID: 1557671181).
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