Hereditary factors as a cause for substance abuse

What does the metabolism of acetaldehyde indicate?

Therefore, if a person has a slower metabolism, acetaldehyde will remain in the body for longer, but if they inherit a gene that means they have a faster metabolism, they will be able to drink more for longer; this ability to be able to drink more, and for longer, puts people with a faster metabolism at a heightened risk of alcoholism.

Why may adoption studies be a better measure to establish cause and effect than twin studies?

The reliability of findings from twin studies is limited simply because we cannot separate the influence of genetics from the influence of the environment and so instead, we can use adoption studies.

What other biological factors affect alcohol abuse?

There are, physical factors that have an influence on alcohol and drug use. It is believed that certain individuals may inherit genes that mean they metabolise ethanol differently in their body. Ethanol breaks down into acetaldehyde inside the body and it's this that makes a person feel nauseous. However, different genes being inherited determine the metabolism of acetaldehyde.

Describe one strength of adoption studies

AO2- Separating the influence of the environment from genetic influence allows psychologists to reliably establish cause and effect and despite excluding environmental factors there is still a correlation, suggesting that genetic influence is an important factor in the starting of alcohol abuse.

What did Schukit find?

About 40% of the sons of alcoholic fathers showed low sensitivity to alcohol and reported low levels of intoxication compared with 10% of the non-alcoholics sons. Ten years later, alcoholism was found in 43% of those who showed the least response to alcohol. This suggests that sensitivity to alcohol is inherited and has an effect on the likelihood of alcoholism and provides further support for a genetic sensitivity to alcohol being inherited.

What concordance rates did McGue find for MZ and DZ twins?

After the pairs of twins were interviewed about their alcohol use, they found that in male monozygotic twins there was a 77% concordance rate and in dizygotic twins a, lower, 54% concordance rate. The male MZ twins showed greater similarity in their alcohol abuse than the DZ twins which is concurrent with their genetic makeup; MZ twins share 100% of their genetic makeup and DZ twins, about 50%.

What did Cloninger do?

Cloninger aimed to investigate the possible inheritance of alcoholism in males. He studied 1724 adopted Swedish males; their alcohol abuse was measured and so was their biological father's (some of which were alcoholics). The drinking habits of their adoptive fathers were also investigated.

What did Cloninger find?

Cloninger found that the son was more likely to abuse alcohol if their biological father did. 18% of adopted sons abused alcohol, as did their biological fathers whereas only 4% of sons whose fathers were not alcohol abusers went on to become alcoholics. This is statistically significant and therefore supports the genetic explanation for alcohol abuse because those participants whose parents are alcoholics have a higher risk of alcoholism suggesting that another factor, outside of the environment, is having an affect; genes.

What evidence is there to suggest that genetics may determine differences in alcohol metabolism?

Evidence for genetics determining differences in alcohol metabolism can be found in different cultures. Oriental races, the Chinese and Japanese, have a genetically based metabolic sensitivity to alcohol and so respond quickly to alcohol with a faster heart rate, nausea and a flushing response known as 'Oriental flush' (Marshall).

What did Schukit do?

He investigated the variance in alcohol sensitivity between sons of alcoholic and non-alcoholic fathers to find out if there is a link to future alcoholism. Over 400, about 20 years-old men took part in an 'alcohol challenge' where they consumed 3 to 5 drinks and then reported their levels of intoxication, they were then followed up with interviews and research into medical records etc. about 10 years later.

Describe how adoption studies are used

In adoption studies children are separated from alcohol parents, usually fathers to avoid the influence of alcohol in the womb, to measure the genetic influence on alcoholism alone.

What evidence is there to suggest that substance abuse may be the result of an interaction of both nature and nurture?

It was also found in the Cloninger study that sons with both biological and adoptive alcoholic fathers had an increased risk of alcoholism. This leads to a conclusion that it could be an interaction of genes and the environment that causes alcoholism and it is not either that solely influences substance abuse.

Describe one study that investigated genetics for alcoholism using twins.

McGue provides support for the genetic explanation for alcohol abuse as it shows that the more closely related a person is to an alcoholic, the higher their risk of developing alcoholism themselves. McGue aimed to find the extent of similarities between male monozygotic and dizygotic twins in diagnoses of alcohol abuse.

Why are genetic models criticised?

One major criticism of genetic models of addiction is that they don't explain why people abuse substances. If a person is genetically programmed to overindulge in drinking, for example, this does not prevent them from experiencing the unpleasant effects of such overindulgence and learning from this.

Does substance abuse run in families?

Substance abuse runs in families but distinguishing whether this is down to genetics or social learning is something psychologists are interested in as it remains difficult to conclusively determine.

What other explanation might account for such concordance rates?

Such high concordance rates can be explained by the twins sharing their environment instead of their shared genes. Twins tend to share experiences like starting school and sharing peer groups and friends. Unlike ordinary siblings, they experience not only the same events, but at the same age e.g. the loss of a loved one. Moreover, twins share a womb at the same time, meaning that if there is a problem during pregnancy they will both be affected by it.

Explain Oriental flush.

These people have low levels of the enzyme that breaks down acetaldehyde, meaning its unpleasant effects are more intense and last longer than normal. This metabolic characteristic acts as protection against heavy drinking as they are biologically predisposed to not drink such large quantities of alcohol. Oriental races, not surprisingly, have some of the lowest levels of alcoholism in the world, suggesting that the metabolism gene affects a person's risk of alcoholism.

The concordance rates for MZ twins are not 100%. What does this suggest?

This suggests that there must be another influential factor in substance abuse as well as the genetic component, for example personality or social and peer influence.

Describe one way in which the possibility that alcoholism can be inherited has been researched.

Twin studies have been used to research inheritance of alcoholism in more depth. Both MZ and DZ twins have been studied but MZ twins are of particular interest because, if a characteristic is inherited, it should be found in both twins as they share 100% of their genetic makeup.