Genetics vs. Environment in Alcoholism

Hawkins, Catalano, and Miller (1992) suggest three general risk factors for alcoholism, two of which are clearly environmental, all three of which could be: 1) home and environment, 2) social norms and 3) child behavioral factors. The first two factors are always environmental in nature whereas the third may often result from or result in a reaction to the environment. The conditions of the family create major components of the environment in which children are raised. Therefore, the relative contribution of genetics versus environment to alcoholism is an issue.

It seems clear that neither genetic factors nor environmental factors can account for the whole story of alcoholism. Both factors interact to determine the individual risk for becoming alcoholic. While family history might reveal a person’s tendency towards becoming an alcoholic, the relative importance and contribution of genetics versus environment has never been adequately resolved. Differences in alcohol metabolizing enzymes and the genes that encode for them are the best understood factors that influence drinking behavior and the risk of alcoholism.

Despite our recognition that some aspects of alcoholism may be inherited, we do not know the genes connected to alcoholism that are passed from one generation to the next. The only ones we can recognize with confidence are those known to be involved with alcohol metabolism in the cell, in particular, the genes that code for the enzyme alcohol dehydrogenase (ADH). Even though statistics reveal that sons and brothers of alcoholics become alcoholic, they are raised in the same environment.

Furthermore, some have noticed that even twins separated at birth and adoptees tend to end up with adoptive parents similar to their birth parents, so environmental factors may be as crucial as, or more crucial than, genetic factors. Ultimately, determining the relative roles of genetics versus environment in contributing to alcoholic behavior or ‘alcoholism,’ whatever the term may mean, have proven to be both difficult and confusing. VII. Nature vs. Nurture The question of genetics versus environment leads directly to the issue of Nature vs.

Nurture. It is known that children of alcoholics are more at risk for becoming alcoholic. The question is, “Does genetics play a greater role than personal choice or other factors in alcoholism? ” Even though both genetics and the environment contribute to alcoholic behavior, we are not certain which plays the greatest role. Does a child learn alcoholic behavior or inherit it from parents. While genes play a role in alcoholic behavior, we cannot assume that genes predispose individuals to alcoholic behavior. Goodwin et al.

(1974) studied drinking problems in adopted males and compared them to males who were not adopted. Their study demonstrated that alcoholic behavior does run in families, but did not determine whether genes or the home environment was the predominant cause of that behavior. Cotton also considered this question in her review without a conclusive decision. VIII. Diseases associated with drinking. Some diseases are clearly associated with drinking, but the habit causes disease. The habit itself is not the disease or a disease and does not result from a disease.

We must consider what diseases are associated with excessive alcohol consumption, how they are associated with excessive consumption and how disease states relate to other habits in order to determine whether excessive drinking itself is a disease. Alcohol consumption raises the levels of triglycerides (fats) in the blood leading to cardiovascular disorders. Therefore, health problems such as high blood pressure and heart failure are not uncommon in individuals who drink excessively. Ironically, some studies have also demonstrated a reduced risk of heart disease connected with wine consumption.

There is also a small relationship between alcohol consumption and cancer, but certainly, liver problems, most notably cirrhosis of the liver, is among the most common risk factors to alcoholics. Ironically, more alcoholics die from tobacco related illnesses such as cancer and heart disease than from chronic liver disease or cirrhosis (2003 A. D. A. M. , Inc. ) In general, excessive alcohol consumption places individuals at greater risk for liver diseases, certain cancers and stroke.

Cirrhosis of the liver is among the most common liver ailments associated with excessive drinking. Cirrhosis results in liver fatal scarring that blocks the flow of blood through the liver and causes it to cease functioning. There is no cure. Although there are many causes of cirrhosis, chronic alcoholism and hepatitis C are the major causes of cirrhosis. This condition generally develops after many years of heavy alcohol consumption. The disease cannot be cured and is often fatal ranking as the twelfth largest cause of death by disease annually in the US. IX. Twin Studies

Since there is a relationship between alcoholic behavior and genetics, one means of better understanding the genetic contribution to such behavior is to consider alcoholic behavior in twins. Twin studies have shown that there is a real connection between alcohol consumption and genetics. (Newman et al, 1937; Shields, 1962; Juel-Nielsen, 1965) While environment certainly plays a role as well, when studies of twins are compared with siblings who lived with alcoholic parents, the presence of the biologically related parent proved to be the only significant factor in predicting alcoholic behavior.

A study of male twins in Finland found that alcoholism could be more readily predicted in than problem drinking in male twins. (Jonsson, 1968) Also, another study of twins concluded that genetics influenced the consumption of large amounts of alcohol more than it influenced non alcohol consumption. (Jonsson, 1968) One important factor in twin studies is when they are separated. Studies that consider this factor indicate that separated twins and non separated twins have similar habits with respect to alcohol consumption (Newman et al.

, 1937; Shields, 1962; Juel-Nielsen, 1965). In general, studies indicate that the need to drink large amounts of alcohol is greater among twins and among children of alcoholics, suggesting that both factors play a role in problem drinking. Distinguishing which factor is of greatest importance is difficult. Pickens et al (1991) found that both males and female identical twins were susceptible to becoming alcoholic than fraternal twins, but male twins were more susceptible than female twins.

Other studies have demonstrated that identical twins generally live in environments that are more similar than fraternal twins but many twin studies do not take this fact into consideration. (McGue, 1991) So the results of some twin studies must be called into question. Ultimately, while the results of twin studies suggest a genetic contribution to alcoholic condition, the results cannot be viewed as conclusive as to genes being the cause of such behavior. X. Adoption Studies

Adoption studies compliment twin studies. These studies compare the family history of adopted children with alcoholic parents to the family history of children adopted by non-alcoholic parents. (Goodwin et al. , 1973; Cadoret et al, 1980; Cloninger, C. R. et al. , 1985) In general, these studies found that adopted children of alcoholics were more likely to become alcoholic themselves, suggesting a role for genes in alcoholism, but many these studies did not rule out environmental factors.

Most studies on adoptees reveal the trends that would be expected if genes play a role in alcoholic behavior, but the evidence was not sufficiently conclusive to attribute alcoholic behavior to genes over environment. (Goodwin et al. , 1974. ; Goodwin et al. , 1973; Cloninger, C. R. et al. , 1981; Bohman, et al. , 1981. ) While these studies imply a role for genes in alcoholic behavior and in the development of the condition, they do not rule out the possibility that other factors, including personal choice, play an equally great as or greater role than other genetics. XI. Genetic Markers

It would certainly be helpful to define alcoholism before discussing the genetic markers associated with the condition, but unfortunately, since there is no consensus definition for alcoholism, we were not been able earlier to provide you with a clear definition. Therefore, it is difficult to label alcoholism as a disease because no disease parameters have been defined for it and all diseases, without exception, have clearly defined parameters. Still, a number of genetic markers for alcoholism or the diseases that arise from excessive alcohol consumption have been uncovered.

Genetic markers are proteins, genes or DNA sequences that are involved with alcoholism and are transmitted from one generation to the next. Despite being redundant, it is important to point out that we are speaking of markers for the habit of over consuming alcohol. To date, we have no genetics markers that can clearly be associated with that habit. However, a number of genetics markers have been associated with the conditions that arise from over consumption and are generally viewed as being associated with ‘alcoholism’.

In what follows, we cannot be absolutely clear what the researchers meant when they attached the genetic traits to ‘alcoholism’. Some genetic markers have been reported. Genetic markers must be sufficiently close on the same chromosome that they do not separate during the development and production of the germ cells for reproduction, a process called gametogenesis. Hill et al. (1988) reported a genetic linkage between alcoholism and the MNS blood group discovered on chromosome 4 in 1927 (Hill et al. , 1988). Another genetic marker was uncovered between alcoholism and the esterase D on chromosome 13 (Tanna et al.

, 1998). Other genetics markers have also been uncovered. For now, we must assume that these genetic markers are connected to the conditions that arise from excessive drinking—conditions that arise after drinking has become entrenched—rather than from the habit of over consumption. The genetics research literature on alcoholism is not always clear on this point. We will assume that these traits do not represent the cause of over consumption and we would prefer to avoid the idea that any genetics traits cause people to drink.

Rather, alcohol consumption is a matter of personal choice. While the genes mentioned may contribute to alcoholic behavior, clearly, they do not cause such behavior. Many people with the genes do not become alcoholics and many without the genes do. Then, of course, there is still the question, never adequately resolved, as to exactly what constitutes being an alcoholic. Is it the behavior of abusive alcohol consumption, certainly not caused by a gene, or the subsequent conditions that arise?

If genes caused a particular behavior, virtually everyone with the genes would also have the behavior and most of those lacking the gene would not. We realize that the presence of genes on a chromosome does not necessarily mean that the gene will be expressed. Some traits dominate over others, and factors of dominance over recessive must be known, but one would certainly consider that the presence of a gene for alcoholism would have some role in our ability to predict the condition. However, personal choice and environment still appear to be more reasonable explanations than genetics for alcoholic behavior.

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